From: | Andres Freund <andres(at)anarazel(dot)de> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <bruce(at)momjian(dot)us>, pgsql-hackers(at)postgresql(dot)org, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Subject: | Re: profiling connection overhead |
Date: | 2010-11-29 17:49:12 |
Message-ID: | 201011291849.12406.andres@anarazel.de |
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Lists: | pgsql-hackers |
On Monday 29 November 2010 18:34:02 Robert Haas wrote:
> On Mon, Nov 29, 2010 at 12:24 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > Hm. A quick test shows that its quite a bit faster if you allocate memory
> > with:
> > size_t s = 512*1024*1024;
> > char *bss = mmap(0, s, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_POPULATE|
> > MAP_ANONYMOUS, -1, 0);
>
> Numbers?
malloc alloc: 43
malloc memset1: 438763
malloc memset2: 98764
total: 537570
mmap alloc: 296065
mmap memset1: 99203
mmap memset2: 100608
total: 495876
But you don't actually need the memset1 in the mmap case as MAP_ANONYMOUS
memory is already zeroed. We could actually use that knowledge even without
MAP_POPULATE if we somehow keep track whether an allocated memory region is
still zeroed.
Taking that into account its:
malloc alloc: 47
malloc memset1: 437819
malloc memset2: 98317
total: 536183
mmap alloc: 292904
mmap memset1: 1
mmap memset2: 99284
total: 392189
I am somewhat reluctant to believe thats the way to go.
Andres
Attachment | Content-Type | Size |
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zero.c | text/x-csrc | 1.5 KB |
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