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Re: [PATCH] calloc should not duplicate malloc logic.
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Siddhesh Poyarekar <siddhesh at redhat dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Wed, 26 Feb 2014 18:24:12 +0100
- Subject: Re: [PATCH] calloc should not duplicate malloc logic.
- Authentication-results: sourceware.org; auth=none
- References: <20140221150417 dot GA4198 at domone dot podge> <20140226143648 dot GA32752 at spoyarek dot pnq dot redhat dot com> <20140226162521 dot GA24933 at domone dot podge> <20140226165123 dot GA6419 at spoyarek dot pnq dot redhat dot com>
On Wed, Feb 26, 2014 at 10:21:23PM +0530, Siddhesh Poyarekar wrote:
> On Wed, Feb 26, 2014 at 05:25:21PM +0100, OndÅej BÃlka wrote:
> > Siddhesh, before you speak you need check the facts. Use a benchmark
> > so you could quantify if it is worth of concern or difference will just
> > disappear in noise.
>
> You're posting a patch and also admitting to a performance regression.
> I'm not sure why you think I should spend my time writing a benchmark
> to refute your patch.
>
I did not said so, I said there could be minor regression and asked if
that is problem. Also there is problem of synchronization as independent
modifications would conflict and I want minimize these issue before they
happen
> > Siddhesh a following program already consumes a gigabyte in rss so your
> > claim is nonsense again.
> >
> > #include <malloc.h>
> > int main()
> > {
> > char *x = calloc (1000000000,1);
> > sleep(1000);
> > }
>
> You haven't understood why this is a bad idea. The pages will have
> been zeroed twice with your patch, once by mmap and again with memset.
>
I understood you perfecly and you are wrong here. Current implementation
also zeroes memory twice as this example demonstrates. Your point is
invalid here.