From: Anton Blanchard <anton@samba.org>
To: Adhemerval Zanella <azanella@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] [RFC] powerpc: Add VDSO version of time
Date: Fri, 19 Apr 2013 08:38:35 +1000 [thread overview]
Message-ID: <20130419083835.37f1c180@kryten> (raw)
In-Reply-To: <5148C2B3.6010408@linux.vnet.ibm.com>
Hi Adhemerval,
> This patch implement the time syscall as vDSO. I have a glibc patch
> to use it as IFUNC (as latest gettimeofday patch). Below the perf
> numbers:
>
> Baseline PPC32: 380 nsec
> Baseline PPC64: 352 nsec
> vdso PPC32: 20 nsec
> vdso PPC64: 20 nsec
Very nice speedup. One small performance improvement:
+1: ld r8,CFG_TB_UPDATE_COUNT(r3)
+ ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3)
+ andi. r0,r8,1 /* pending update ? loop */
+ bne- 1b
Since you are only reading one long you shouldn't need to check the
update count and loop, you will always see a consistent value. The
system call version of time() just does an unprotected load for example.
> I focused on 64 bit kernel, do I need to provide a scheme for 32 bits
> as well?
>
> Any tips, advices, comments?
With the above change and with Michael's comments covered (decent
changelog entry and Signed-off-by):
Acked-by: Anton Blanchard <anton@samba.org>
Anton
next prev parent reply other threads:[~2013-04-18 22:38 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-19 19:55 [PATCH] [RFC] powerpc: Add VDSO version of time Adhemerval Zanella
2013-03-20 5:00 ` Benjamin Herrenschmidt
2013-03-21 13:40 ` Adhemerval Zanella
2013-03-26 17:32 ` Adhemerval Zanella
2013-04-04 19:22 ` Adhemerval Zanella
2013-04-05 6:21 ` Michael Ellerman
2013-04-05 18:49 ` Adhemerval Zanella
2013-04-08 14:05 ` Adhemerval Zanella
2013-04-18 5:58 ` Michael Ellerman
2013-04-18 22:38 ` Anton Blanchard [this message]
2013-04-22 19:29 ` Adhemerval Zanella
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130419083835.37f1c180@kryten \
--to=anton@samba.org \
--cc=azanella@linux.vnet.ibm.com \
--cc=linuxppc-dev@lists.ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).