From: David Disseldorp <ddiss@suse.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org,
willy@infradead.org
Subject: Re: [PATCH 1/5] initramfs: move unnecessary memcmp from hot path
Date: Thu, 23 Sep 2021 09:33:23 +0200 [thread overview]
Message-ID: <20210923093323.5632a534@suse.de> (raw)
In-Reply-To: <YUu91kH8kOcVHxyb@zeniv-ca.linux.org.uk>
On Wed, 22 Sep 2021 23:35:50 +0000, Al Viro wrote:
> On Wed, Sep 22, 2021 at 01:52:18PM +0200, David Disseldorp wrote:
> > do_header() is called for each cpio entry and first checks for "newc"
> > magic before parsing further. The magic check includes a special case
> > error message if POSIX.1 ASCII (cpio -H odc) magic is detected. This
> > special case POSIX.1 check needn't be done in the hot path, so move it
> > under the non-newc-magic error path.
>
> You keep refering to hot paths; do you have any data to support that
> assertion?
The code-path is run for every single initramfs entry on every single
boot. Calling that "hot" is reasonable IMO.
> How much does that series buy you on average, and what kind of dispersion
> do you get before and after it?
I withdrew the perf claims for this patch after you rightly pointed out
that my previous numbers weren't statistically significant. After doing
further checks I noticed that there was more to be gained via the
INITRAMFS_PRESERVE_MTIME changes. Numbers for extraction performance
with and without mtime preservation can be found in [PATCH 5/5] of this
series.
> I'm not saying I hate the patches themselves, but those references in commit
> messages ping my BS detectors every time I see them ;-/
I'll try harder to strip anything that might be considered buzzwordy in
future, sorry.
Cheers, David
prev parent reply other threads:[~2021-09-23 7:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-22 11:52 [PATCH 1/5] initramfs: move unnecessary memcmp from hot path David Disseldorp
2021-09-22 11:52 ` [PATCH 2/5] initramfs: print helpful cpio error on "crc" magic David Disseldorp
2021-09-22 11:52 ` [PATCH v2 3/5] docs: remove mention of "crc" cpio format support David Disseldorp
2021-09-22 11:52 ` [PATCH 4/5] initramfs: use do_utime() wrapper consistently David Disseldorp
2021-09-22 11:52 ` [PATCH 5/5] initramfs: add INITRAMFS_PRESERVE_MTIME Kconfig option David Disseldorp
2021-09-22 23:28 ` [PATCH 1/5] initramfs: move unnecessary memcmp from hot path Chaitanya Kulkarni
2021-09-23 7:43 ` David Disseldorp
2021-09-22 23:35 ` Al Viro
2021-09-22 23:51 ` Chaitanya Kulkarni
2021-09-23 7:33 ` David Disseldorp [this message]
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