From: Judith Lebzelter <judith@osdl.org> To: Suparna Bhattacharya <suparna@in.ibm.com> Cc: linux-aio@kvack.org, linux-osdl@osdl.org Subject: [linux-osdl] Re: OSDL aio-stress result on buffered reads for recent AIO patch set Date: Wed, 04 Aug 2004 11:54:10 -0700 On Thu, 29 Jul 2004, Suparna Bhattacharya wrote: > Hello Judith, > > Thanks for reporting this. Sorry, I was travelling and couldn't > respond earlier. > > Could you try a run with a single file and let me know if you > still see inconsistencies ? The AIO readahead congestion message > might indicate saturation of the queue during readaheads, making > the code fallback to a slow path, but I'm not entirely sure. Hello Suparna; This took a while to get to them due to our STP release last week, but I finally did run the tests on your aio patch set again with one 4Gbyte file. aio-stress Buffered Reads stp2-000 295650 295649 295646 sequential reads: 43.89 MB/s 43.88 MB/s 44.07 MB/s random reads 32.39 MB/s 32.25 MB/s 32.21 MB/s stp2-003 295654 295645 sequential reads: 46.73 MB/s 1.23 MB/s random reads 32.12 MB/s 32.14 MB/s Using only one file, the results are more consistant, except for sequential reads in test 295645 on host stp2-003, which took inexpectedly long. I used these settings: file size 4096MB, record size 64KB, depth 64, ios per iteration 8 max io_submit 8, buffer alignment set to 4KB threads 1 files 1 contexts 1 context offset 2MB verification off The host has 1G RAM. The filesystem is ext2. I also still saw the 'AIO readahead congestion' message for at least one run. > > Your options are reasonable from a stress testing perspective, > though typically for performance testing it makes more sense to > have individual aio-stress runs for each of the modes -o1 to -o3, > explicitly, (typically both the non-cached and cached cases) so > that results aren't affected by the history of earlier accesses > or readahead state on the file descriptor. I just changed this and am testing it with some more runs. I am running a few with the same settings as that last data set to do a compare. Judith > > Regards > Suparna > > On Thu, Jul 22, 2004 at 03:12:33PM -0700, Judith Lebzelter wrote: > > Hello; > > > > I have run aio-stress on the OSDL conduit, which includes the recent > > aio patch set from Suparna Bhattacharya on linux-2.6.7. I have found > > inconsistant throughput for buffered sequential and random reads. > > > > On 2-CPU/1G/ext2 run with 4 X 1G files: > > 2.6.7^ aio-patch* aio-patch** aio-patch*** > > run 1 run 2 run 3 > > Seq Read 24.36 MB/s 45.83 MB/s 28.27 MB/s 1.25 MB/s > > Ran Read 7.14 MB/s 1.33 MB/s 4.08 MB/s 13.71 MB/s > > > > Raw data: > > ^http://khack.osdl.org/stp/295153/results/runlog.buffer.txt > > ^^http://khack.osdl.org/stp/295109/results/runlog.buffer.txt > > *http://khack.osdl.org/stp/295135/results/runlog.buffer.txt > > **http://khack.osdl.org/stp/295132/results/runlog.buffer.txt > > ***http://khack.osdl.org/stp/295110/results/runlog.buffer.txt > > > > > > For the patched kernel run 295110, the Sequential read throughput > > was very inconsistant across files. For run 295135 the Random > > reads were inconsistant across files. In general runs do not > > seem reproducible. > > > > However, for the linux-2.6.7 the throughput is generally consistant > > across files for a single run, and reproducible across seperate > > runs. > > > > I see similar inconsistancy on the 1CPU host and the 4CPU host: > > http://khack.osdl.org/stp/295107/results/runlog.buffer.txt > > http://khack.osdl.org/stp/295113/results/runlog.buffer.txt > > > > > > I am seeing a message on the console 'AIO readahead congestion' over and > > over again while the test is running for at least some runs. > > > > Are my options realistic? Or any other suggestions?? I plan to run > > a few more tests on other filesystem types and with oprofile. > > > > Regards; > > > > Judith Lebzelter > > OSDL > > > > > > -- > > To unsubscribe, send a message with 'unsubscribe linux-aio' in > > the body to majordomo@kvack.org. For more info on Linux AIO, > > see: http://www.kvack.org/aio/ > > Don't email: <a href=mailto:"aart@kvack.org">aart@kvack.org</a> > >