This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [RFC][BZ #16549, #16410] Remove pthread_(cond)wait assembly implementations?
- From: Roland McGrath <roland at hack dot frob dot com>
- To: Rich Felker <dalias at aerifal dot cx>
- Cc: OndÅej BÃlka <neleai at seznam dot cz>, libc-alpha at sourceware dot org
- Date: Tue, 11 Feb 2014 10:16:53 -0800 (PST)
- Subject: Re: [RFC][BZ #16549, #16410] Remove pthread_(cond)wait assembly implementations?
- Authentication-results: sourceware.org; auth=none
- References: <20140211172324 dot GA31923 at domone dot podge> <20140211172720 dot 52ABB7445F at topped-with-meat dot com> <20140211180758 dot GB15627 at brightrain dot aerifal dot cx>
> Is there any record of this having been measured at the time they were
> added? I don't have any evidence to refute the claim that the asm
> performed measurably better, but I also find it a bit doubtful.
I'm sure that it was measured informally. But I'm also sure that there are
no useful records to be had. pthread_cond_{timed,}wait are unlike most
others in that they are not (in sensible programs) called at all for
uncontended cases, so it's almost certain that (modulo quick races) they
will be making the system call. So indeed it is hard to see how this case
could matter. But we still must be circumspect and give the benefit of the
doubt that the decisions made in the past had merit and should not be
dismissed out of hand.