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  • Calculating CPU frequency in C with RDTSC always returns 0

    - by Nazgulled
    Hi, The following piece of code was given to us from our instructor so we could measure some algorithms performance: #include <stdio.h> #include <unistd.h> static unsigned cyc_hi = 0, cyc_lo = 0; static void access_counter(unsigned *hi, unsigned *lo) { asm("rdtsc; movl %%edx,%0; movl %%eax,%1" : "=r" (*hi), "=r" (*lo) : /* No input */ : "%edx", "%eax"); } void start_counter() { access_counter(&cyc_hi, &cyc_lo); } double get_counter() { unsigned ncyc_hi, ncyc_lo, hi, lo, borrow; double result; access_counter(&ncyc_hi, &ncyc_lo); lo = ncyc_lo - cyc_lo; borrow = lo > ncyc_lo; hi = ncyc_hi - cyc_hi - borrow; result = (double) hi * (1 << 30) * 4 + lo; return result; } However, I need this code to be portable to machines with different CPU frequencies. For that, I'm trying to calculate the CPU frequency of the machine where the code is being run like this: int main(void) { double c1, c2; start_counter(); c1 = get_counter(); sleep(1); c2 = get_counter(); printf("CPU Frequency: %.1f MHz\n", (c2-c1)/1E6); printf("CPU Frequency: %.1f GHz\n", (c2-c1)/1E9); return 0; } The problem is that the result is always 0 and I can't understand why. I'm running Linux (Arch) as guest on VMware. On a friend's machine (MacBook) it is working to some extent; I mean, the result is bigger than 0 but it's variable because the CPU frequency is not fixed (we tried to fix it but for some reason we are not able to do it). He has a different machine which is running Linux (Ubuntu) as host and it also reports 0. This rules out the problem being on the virtual machine, which I thought it was the issue at first. Any ideas why this is happening and how can I fix it?

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  • NFOP performance problem

    - by Jay Stevens
    We're using NFOP in a project (C#, ASP.NET 2.0) to ultimately return PDF files to the user. The process currently goes like this: Stored Procedure - XML XML - XSLT - XSL-FO XSL-FO - NFOP - PDF This works fine, the PDF is generated BEAUTIFULLY. The problem is that it takes 300+ seconds to do it. The ANTS profiler indicates that the problem is sitting in the driver.run() method inside of NFOP. It's not like this is a gargantuan amount of data, the size of the xsl-fo source going into the nfop driver object is ~980k. What's the most likely source and resolution of this problem? ANY hints or tips or answers are most appreciated, we were supposed to head to VA scan at 11 am. :|

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  • Entity Framework Performance Inconsistency Compared to Sql Management Studio

    - by AndyV
    I'm getting timeouts with a very basic EF statement. I'm simply doing a select from a single table with a Entity.Title.StartsWith("test") and a .Take(25). When I run this for a search that returns no results I get a timeout. If I profile and grab the sql statement it looks fine, and if I run that sql in Management Studio it runs in a fraction of a second! Why would the same query run sub-second in Management Studio and timeout when generated by EF and called from an Asp.Net app?

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  • Problem performance datawarehouse with lots of indexes

    - by Lieven Cardoen
    Our product takes tests of some 350 candidates at the same time. At the end of the test, results for each candidate are moved to a datawarehouse full of indexes on it. For each test there's some 400 records to be entered in datawarehouse. So 400 x 350 is a lot of records. If there are not much records in the datawarehouse, all goes well. But if there are already lots of records in the datawarehouse, then a lot of inserts fail... Is there a way to have indexes that are only rebuild at the end of the day or isn't that the real problem? Or how would you solve this?

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  • Is my understanding of "select distinct" correct?

    - by paxdiablo
    We recently discovered a performance problem with one of our systems and I think I have the fix but I'm not certain my understanding is correct. In simplest form, we have a table blah into which we accumulate various values based on a key field. The basic form is: recdate date rectime time system varchar(20) count integer accum1 integer accum2 integer There are a lot more accumulators than that but they're all of the same form. The primary key is made up of recdate, rectime and system. As values are collected to the table, the count for a given recdate/rectime/system is incremented and the values for that key are added to the accumulators. That means the averages can be obtained by using accumN / count. Now we also have a view over that table specified as follows: create view blah_v ( recdate, rectime, system, count, accum1, accum2 ) as select distinct recdate, rectime, system, count, value (case when count > 0 then accum1 / count end, 0), value (case when count > 0 then accum2 / count end, 0) from blah; In other words, the view gives us the average value of the accumulators rather than the sums. It also makes sure we don't get a divide-by-zero in those cases where the count is zero (these records do exist and we are not allowed to remove them so don't bother telling me they're rubbish - you're preaching to the choir). We've noticed that the time difference between doing: select distinct recdate from XX varies greatly depending on whether we use the table or the view. I'm talking about the difference being 1 second for the table and 27 seconds for the view (with 100K rows). We actually tracked it back to the select distinct. What seems to be happening is that the DBMS is actually loading all the rows in and sorting them so as to remove duplicates. That's fair enough, it's what we stupidly told it to do. But I'm pretty sure the fact that the view includes every component of the primary key means that it's impossible to have duplicates anyway. We've validated the problem since, if we create another view without the distinct, it performs at the same speed as the underlying table. I just wanted to confirm my understanding that a select distinct can not have duplicates if it includes all the primary key components. If that's so, then we can simply change the view appropriately.

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  • F# performance question: what is the compiler doing?

    - by Stephen Swensen
    Referencing this code: http://stackoverflow.com/questions/2840714/f-static-member-type-constraints/2842037#2842037 Why is, for example, [1L..100000L] |> List.map (fun n -> factorize gL n) significantly slower than [1L..100000L] |> List.map (fun n -> factorize (G_of 1L) n) By looking at Reflector, I can see that the compiler is treating each of these in very different ways, but there is too much going on for me to decipher the essential difference. Naively I assumed the former would perform better than the later because gL is precomputed whereas G_of 1L has to be computed 100,000 times (at least it appears that way).

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  • Datastore performance, my code or the datastore latency

    - by fredrik
    I had for the last month a bit of a problem with a quite basic datastore query. It involves 2 db.Models with one referring to the other with a db.ReferenceProperty. The problem is that according to the admin logs the request takes about 2-4 seconds to complete. I strip it down to a bare form and a list to display the results. The put works fine, but the get accumulates (in my opinion) way to much cpu time. #The get look like this: outputData['items'] = {} labelsData = Label.all() for label in labelsData: labelItem = label.item.name if labelItem not in outputData['items']: outputData['items'][labelItem] = { 'item' : labelItem, 'labels' : [] } outputData['items'][labelItem]['labels'].append(label.text) path = os.path.join(os.path.dirname(__file__), 'index.html') self.response.out.write(template.render(path, outputData)) #And the models: class Item(db.Model): name = db.StringProperty() class Label(db.Model): text = db.StringProperty() lang = db.StringProperty() item = db.ReferenceProperty(Item) I've tried to make it a number of different way ie. instead of ReferenceProperty storing all Label keys in the Item Model as a db.ListProperty. My test data is just 10 rows in Item and 40 in Label. So my questions: Is it a fools errand to try to optimize this since the high cpu usage is due to the problems with the datastore or have I just screwed up somewhere in the code? ..fredrik

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  • MySQL index building performance

    - by Christian
    I tried to build an index over a two columns of a 30,000,000 entry database. I canceled the process after ~60hr as it didn't seem to work. For some reason MySQL takes only 22 mb ram instead of using the RAM fully. Is index building an operation that needs no Ram or is there some way to tell MySQL to use more RAM to be faster?

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  • JPA - Performance with using multiple entity manager

    - by Nguyen Tuan Linh
    My situation is: The code is not mine I have two kinds of database: one is Dad, one is Son. In Dad, I have a table to store JNDI name. I will look up Dad using JNDI, create entity manager, and retrieve this table. From these retrieved JNDI names, I will create multiple entity managers using multiple Son databases. The problem is: Son have thousands of entities. It takes each Son database around 10 minutes to load all entities. If there is 4 Son databases, it will be 40 minutes. My question: Is there any way to load all entities and use them for all entity manager? Please look at the code below For each Son JNDI: Map<String, String> puSonProperties = new HashMap<String, String>(); puSonProperties.put("javax.persistence.jtaDataSource", sonJndi); EntityManagerFactory emf = Persistence.createEntityManagerFactory("PUSon", puSonProperties); PUSon - All of them use the same persistence unit log.info("Verify entity manager for son: {0} - {1}", sonCode, emSon.find(Son_configuration.class, 0) != null ? "ok" : "failed!"); This is the actual code where the loading of all entities begins. 10 mins.

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  • Raphael JS image animation performance.

    - by michael
    Hi, I'm trying to create an image animation using Raphael JS. I want the effect of a bee moving randomly across the page, I've got a working example but it's a bit "jittery", and I'm getting this warning in the console: "Resource interpreted as image but transferred with MIME type text/html" I'm not sure if the warning is causing the "jittery" movement or its just the way I approached it using maths. If anyone has a better way to create the effect, or improvements please let me know. I have a demo online here and heres my javascript code: function random(min, max) { return Math.floor(Math.random() * (max - min + 1)) + min; } function BEE(x, y, scale) { this.x = x; this.y = y; this.s = scale; this.paper = Raphael("head", 915, 250); this.draw = function() { this.paper.clear(); this.paper.image("bee.png", this.x, this.y, 159*this.s, 217*this.s); } this.update = function() { var deg = random(-25, 25); var newX = Math.cos(Raphael.rad(deg)) * 2; var newY = Math.sin(Raphael.rad(deg)) * 2; this.x += newX; this.y += newY; if( this.x > 915) { this.x = 0; } if( this.y > 250 || this.y < 0 ) { this.y = 125; } } } $(document).ready(function() { var bee = new BEE(100, 150, 0.4); var timer = setInterval(function(){ bee.draw(); bee.update(); }, 15); }

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  • Slow (to none) performance on SQL 2005 after attaching SQL 2000 database

    - by ploft
    Issue: Using the detach/attach SQL database from a SQL 2000 SP4 instance to a much beefier SQL 2005 SP2 server. Run reindex, reorganize and update statistics a couple of times, but without any success. Queries on SQL 2000 took about 1-2 sec. to complete, now the same queries take 2-3 min on the SQL 2005 (and even 2008 - tested it there also). Have looked at the execution plans and the overall percent matches or are alike on each server.

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  • clam anti-virus is slowing down my server performance

    - by Scarface
    Hey guys, I just installed clam av http://sourceforge.net/projects/php-clamav/ for scanning file uploads on my linux VPN running php. The problem is that for some reason just initiating the extension in the php ini file slows down my entire network. Regular requests such as changing pages that should take less than 1 second take 5. Has anyone ever experienced this before or have a good virus scanning alternative for scanning file uploads? extension=clamav.so [clamav] clamav.dbpath="/usr/share/clamav" clamav.keeptmp=20 clamav.maxreclevel=16 clamav.maxfiles=10000 clamav.maxfilesize=26214400 clamav.maxscansize=104857600 clamav.keeptmp=0

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  • NSURLConnection on simulator and iphone performance issues

    - by Nava Carmon
    I'm experiencing a weird problem and i wonder if anybody else has noticed this: I'm using NSURLConnection as it appears in apple's examples to get xml files from a certain server - pretty straight forward. And most of time it works, but sometimes it's just stuck after initialing and don't get into connection's delegate methods. I'm working with WiFi & 3G and the same server all the time. When it comes to didFailWithError i see that mostly it was a timeout error. When I enter same link in Safari it takes a second to bring data. And after another trial I can access the link. What might be the reason for such a weird behavior? How can I improve it? What is the role of cache policy with NSURLConnection? Thanks, Nava

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  • How to pass ctor args in Activator.CreateInstance?

    - by thames
    I need a performance enhanced Activator.CreateInstance() and came across this article by Miron Abramson that uses a factory to create the instance in IL and then cache it. (I've included code below from Miron Abramson's site in case it somehow disappears). I'm new to IL Emit code and anything beyond Activator.CreateInstance() for instantiating a class and any help would be much appreciative. My problem is that I need to create an instance of an object that takes a ctor with a parameter. I see there is a way to pass in the Type of the parameter, but is there a way to pass in the value of the ctor parameter as well? If possible, I would like to use a method similar to CreateObjectFactory<T>(params object[] constructorParams) as some objects I want to instantiate may have more than 1 ctor param. // Source: http://mironabramson.com/blog/post/2008/08/Fast-version-of-the-ActivatorCreateInstance-method-using-IL.aspx public static class FastObjectFactory { private static readonly Hashtable creatorCache = Hashtable.Synchronized(new Hashtable()); private readonly static Type coType = typeof(CreateObject); public delegate object CreateObject(); /// /// Create an object that will used as a 'factory' to the specified type T /// public static CreateObject CreateObjectFactory() where T : class { Type t = typeof(T); FastObjectFactory.CreateObject c = creatorCache[t] as FastObjectFactory.CreateObject; if (c == null) { lock (creatorCache.SyncRoot) { c = creatorCache[t] as FastObjectFactory.CreateObject; if (c != null) { return c; } DynamicMethod dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + t.Name, typeof(object), null, t); ILGenerator ilGen = dynMethod.GetILGenerator(); ilGen.Emit(OpCodes.Newobj, t.GetConstructor(Type.EmptyTypes)); ilGen.Emit(OpCodes.Ret); c = (CreateObject)dynMethod.CreateDelegate(coType); creatorCache.Add(t, c); } } return c; } } Update to Miron's code from commentor on his post 2010-01-11 public static class FastObjectFactory2<T> where T : class, new() { public static Func<T> CreateObject { get; private set; } static FastObjectFactory2() { Type objType = typeof(T); var dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + objType.Name, objType, null, objType); ILGenerator ilGen = dynMethod.GetILGenerator(); ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(Type.EmptyTypes)); ilGen.Emit(OpCodes.Ret); CreateObject = (Func<T>) dynMethod.CreateDelegate(typeof(Func<T>)); } }

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  • Very slow remote page load performance in QtWebKit (Windows)

    - by Gil
    I get very slow load times on QtWebKit on Windows 7, through ADSL. I am using the Qt Demo Browser, on a Core2 Quad, 64 bit Windows 7, 4GB ram, 2gb processor. through a VPN. Simplest example: google search page takes ~18 seconds to load, compared to 2.5 on Chrome (cash cleared). On larger pages, with scripts etc. it is worse. I tried Qt 4.6 and also the Qt 4.7 beta, but don't see any difference. I see the same results with Arora browser. Are there any settings, or patches that can be applied to fix this? Thanks

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  • How to improve performance of non-scalar aggregations on denormalized tables

    - by The Lazy DBA
    Suppose we have a denormalized table with about 80 columns, and grows at the rate of ~10 million rows (about 5GB) per month. We currently have 3 1/2 years of data (~400M rows, ~200GB). We create a clustered index to best suit retrieving data from the table on the following columns that serve as our primary key... [FileDate] ASC, [Region] ASC, [KeyValue1] ASC, [KeyValue2] ASC ... because when we query the table, we always have the entire primary key. So these queries always result in clustered index seeks and are therefore very fast, and fragmentation is kept to a minimum. However, we do have a situation where we want to get the most recent FileDate for every Region, typically for reports, i.e. SELECT [Region] , MAX([FileDate]) AS [FileDate] FROM HugeTable GROUP BY [Region] The "best" solution I can come up to this is to create a non-clustered index on Region. Although it means an additional insert on the table during loads, the hit isn't minimal (we load 4 times per day, so fewer than 100,000 additional index inserts per load). Since the table is also partitioned by FileDate, results to our query come back quickly enough (200ms or so), and that result set is cached until the next load. However I'm guessing that someone with more data warehousing experience might have a solution that's more optimal, as this, for some reason, doesn't "feel right".

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  • Is I/O Completion ports(Windows) or Asynchronous I/O (AIO) will improve performance of multithreaded

    - by Naga
    Hi, I want to use I/O Completion ports for Windows and Asynchronous I/O (AIO) for solaris and Linux versions of my server application. The application server is multithreaded and it can accept lot of concurrent TCP connections and can process many requests per conenction. Every request will be handled by seperate detached thread. Is this criteria well enough to use the latest AIO?. Is there any standardization using which one code can be used to all platforms. Thanks, Naga

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  • Unexpected performance curve from CPython merge sort

    - by vkazanov
    I have implemented a naive merge sorting algorithm in Python. Algorithm and test code is below: import time import random import matplotlib.pyplot as plt import math from collections import deque def sort(unsorted): if len(unsorted) <= 1: return unsorted to_merge = deque(deque([elem]) for elem in unsorted) while len(to_merge) > 1: left = to_merge.popleft() right = to_merge.popleft() to_merge.append(merge(left, right)) return to_merge.pop() def merge(left, right): result = deque() while left or right: if left and right: elem = left.popleft() if left[0] > right[0] else right.popleft() elif not left and right: elem = right.popleft() elif not right and left: elem = left.popleft() result.append(elem) return result LOOP_COUNT = 100 START_N = 1 END_N = 1000 def test(fun, test_data): start = time.clock() for _ in xrange(LOOP_COUNT): fun(test_data) return time.clock() - start def run_test(): timings, elem_nums = [], [] test_data = random.sample(xrange(100000), END_N) for i in xrange(START_N, END_N): loop_test_data = test_data[:i] elapsed = test(sort, loop_test_data) timings.append(elapsed) elem_nums.append(len(loop_test_data)) print "%f s --- %d elems" % (elapsed, len(loop_test_data)) plt.plot(elem_nums, timings) plt.show() run_test() As much as I can see everything is OK and I should get a nice N*logN curve as a result. But the picture differs a bit: Things I've tried to investigate the issue: PyPy. The curve is ok. Disabled the GC using the gc module. Wrong guess. Debug output showed that it doesn't even run until the end of the test. Memory profiling using meliae - nothing special or suspicious. ` I had another implementation (a recursive one using the same merge function), it acts the similar way. The more full test cycles I create - the more "jumps" there are in the curve. So how can this behaviour be explained and - hopefully - fixed? UPD: changed lists to collections.deque UPD2: added the full test code UPD3: I use Python 2.7.1 on a Ubuntu 11.04 OS, using a quad-core 2Hz notebook. I tried to turn of most of all other processes: the number of spikes went down but at least one of them was still there.

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  • IE performance issues with offsetHeight and offsetWidth

    - by Paul
    I have a site that grabs the response text from an AJAX call and does 'innerHTML' on a div that is going to contain it. After I do the 'innerHTML' I process the DIV by traversing the whole hierarchy of nodes and grabbing their [offsetWidth/offsetHeight] to do some operations with it. Why not css style width/height? because sometimes those values are not available since I don't control what is coming from the AJAX response, plus I want the real box dimensions including borders/scrolls/padding. On large injections (let's say 7,000 new DOM elements) IE takes way longer time than FF/Safari just to get this [offsetWidth/offsetHeight], actually if I wasn't doing injection but just render the contents of the HTML in the browser and processing it, it would be much faster. But that is not an option since I have to inject it on a div that will contain it. Anybody has deal with this kind of issue before? is there an alternative to innerHTML, I have try using documentFragment to inject and process and the move it to the div and still I don't see much gain. How can I get the values that are available with [offsetWidth/offsetHeight]? Thanks a bunch for any suggestions. Paul

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  • SQL Server insert performance

    - by Jose
    I have an insert query that gets generated like this INSERT INTO InvoiceDetail (LegacyId,InvoiceId,DetailTypeId,Fee,FeeTax,Investigatorid,SalespersonId,CreateDate,CreatedById,IsChargeBack,Expense,RepoAgentId,PayeeName,ExpensePaymentId,AdjustDetailId) VALUES(1,1,2,1500.0000,0.0000,163,1002,'11/30/2001 12:00:00 AM',1116,0,550.0000,850,NULL,@ExpensePay1,NULL); DECLARE @InvDetail1 INT; SET @InvDetail1 = (SELECT @@IDENTITY); This query is generated for only 110K rows. It takes 30 minutes for all of these query's to execute I checked the query plan and the largest % nodes are A Clustered Index Insert at 57% query cost which has a long xml that I don't want to post. A Table Spool which is 38% query cost <RelOp AvgRowSize="35" EstimateCPU="5.01038E-05" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimateRows="1" LogicalOp="Eager Spool" NodeId="80" Parallel="false" PhysicalOp="Table Spool" EstimatedTotalSubtreeCost="0.0466109"> <OutputList> <ColumnReference Database="[SkipPro]" Schema="[dbo]" Table="[InvoiceDetail]" Column="InvoiceId" /> <ColumnReference Database="[SkipPro]" Schema="[dbo]" Table="[InvoiceDetail]" Column="InvestigatorId" /> <ColumnReference Column="Expr1054" /> <ColumnReference Column="Expr1055" /> </OutputList> <Spool PrimaryNodeId="3" /> </RelOp> So my question is what is there that I can do to improve the speed of this thing? I already run ALTER TABLE TABLENAME NOCHECK CONSTRAINTS ALL Before the queries and then ALTER TABLE TABLENAME NOCHECK CONSTRAINTS ALL after the queries. And that didn't shave off hardly anything off of the time. Know I am running these queries in a .NET application that uses a SqlCommand object to send the query. I then tried to output the sql commands to a file and then execute it using sqlcmd, but I wasn't getting any updates on how it was doing, so I gave up on that. Any ideas or hints or help?

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  • MYSQL: Simplify this Query for better performance

    - by Treby
    How can i simplify this code. coz this uses subquerying SELECT ub.id_product as c_pid,DATE(ub.datetime_prchs)AS datePurchased,cb.bookname, (SELECT GROUP_CONCAT(c.userid ORDER BY c.userid ASC SEPARATOR ', ') FROM user_books ub INNER JOIN campus_bookinfo cb ON ub.id_product=cb.idx_campus_bookinfo LEFT JOIN customer c ON ub.id_customer=c.id_customer WHERE ub.id_product = c_pid )as buyer, cb.iAmount FROM user_books ub INNER JOIN campus_bookinfo cb ON ub.id_product=cb.idx_campus_bookinfo LEFT JOIN customer c ON ub.id_customer=c.id_customer WHERE ub.id_customer = 29 GROUP BY bookname ORDER BY ub.datetime_prchs I need a better code for the same output.. Thanks in advance

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