We are building our application as a 32-bit entity on both Linux and
Solaris, so our
comparison should be apples to apples. Does anyone happen to know what the
bug id of the small malloc issue is? I searched the opensolaris bug
database, but
wasn't able to dig this up.
Thanks,
- Ryan
On Thu, May 1, 2008 at 4:33 PM, <johansen at sun.com> wrote:
> Part of the problem is that these allocations are very small:
>
> # dtrace -n 'pid$target::malloc:entry { @a["allocsz"] = quantize(arg0); }'
> -c /tmp/xml
>
> allocsz
> value ------------- Distribution ------------- count
> 1 | 0
> 2 | 300000
> 4 |@@@@@ 4700005
> 8 |@@ 1600006
> 16 |@@@@@ 4300015
> 32 |@@@@@@@@@@@@@@@@@@@@@@@@@@@ 24000006
> 64 | 200001
> 128 | 400001
> 256 | 100000
> 512 | 0
> 1024 | 100000
> 2048 | 100000
> 4096 | 0
> 8192 | 100000
> 16384 | 0
>
> After seeing this, I took a look at the exact breakdown of the
> allocation sizes:
>
> # dtrace -n 'pid$target::malloc:entry {...@a[arg0] = count();}' -c /tmp/xml
>
> 12 1
> 96 1
> 200 1
> 21 100000
> 43 100000
> 44 100000
> 51 100000
> 61 100000
> 75 100000
> 88 100000
> 128 100000
> 147 100000
> 181 100000
> 220 100000
> 440 100000
> 1024 100000
> 2048 100000
> 8194 100000
> 8 100001
> 52 100001
> 6 100002
> 36 100004
> 24 100005
> 33 200000
> 4 200001
> 17 200001
> 9 200003
> 3 300000
> 10 300000
> 13 300000
> 14 300000
> 25 300000
> 28 400000
> 11 400001
> 20 700009
> 40 900000
> 5 900001
> 16 2500000
> 7 3500001
> 48 3800001
> 60 18500000
>
> The most frequent malloc call is to allocate 60 bytes. I believe that
> we have a known issue with small mallocs on Solaris. There's a bug open
> for this somewhere; however, I can't find it's number at the moment.
>
> Another problem that you may have run into is the 32-bit versus 64-bit
> compilation problem. I was able to shave about 10 seconds off my
> runtime by compiling your testcase as a 64-bit app instead of a 32-bit
> one:
>
>
> $ gcc -O3 -o xml `/usr/bin/xml2-config --libs --cflags` xml.c
> $ file xml
> xml: ELF 32-bit LSB executable 80386 Version 1 [FPU], dynamically
> linked, not stripped, no debugging information available
> $ ./xml
> 100000 iter in 22.749836 sec
>
> versus:
>
> $ gcc -m64 -O3 -o xml `/usr/bin/xml2-config --libs --cflags` xml.c
> $ file xml
> xml: ELF 64-bit LSB executable AMD64 Version 1, dynamically
> linked, not stripped, no debugging information available
> $ ./xml
> 100000 iter in 13.785916 sec
>
>
> -j
>
>
>
> On Wed, Apr 30, 2008 at 06:44:31PM -0400, Matty wrote:
>
>
> > On Wed, Apr 30, 2008 at 6:26 PM, David Lutz <David.Lutz at sun.com> wrote:
> > > If your application is single threaded, you could try using the
> > > bsdmalloc library. This is a fast malloc, but it is not multi-thread
> > > safe and will also tend to use more memory than the default
> > > malloc. For a comparison of different malloc libraries, look
> > > at the NOTES section at the end of umem_alloc(3MALLOC).
> > >
> > > I got the following result with your example code:
> > >
> > >
> > > $ gcc -O3 -o xml `/usr/bin/xml2-config --libs --cflags` xml.c
> > > $ ./xml
> > > 100000 iter in 21.445672 sec
> > > $
> > > $ gcc -O3 -o xml `/usr/bin/xml2-config --libs --cflags` xml.c
> -lbsdmalloc
> > > $ ./xml
> > > 100000 iter in 12.761969 sec
> > > $
> > >
> > > I got similar results using Sun Studio 12.
> > >
> > > Again, bsdmalloc is not multi-thread safe, so use it with caution.
> >
> > Thanks David. Does anyone happen to know why the memory allocation
> > libraries in Solaris are so much slower than their Linux counterparts? If
> > the various malloc implementations were a second or two slower, I could
> > understand. But they appear to be 10 - 12 seconds slower in our specific
> > test case, which seems kinda odd.
> >
> > Thanks,
> > - Ryan
>
>
> > _______________________________________________
> > perf-discuss mailing list
> > perf-discuss at opensolaris.org
>
