From: Denis Efremov <efremov@ispras.ru>
To: akpm@linux-foundation.org
Cc: Denis Efremov <efremov@ispras.ru>,
Akinobu Mita <akinobu.mita@gmail.com>, Jan Kara <jack@suse.cz>,
linux-kernel@vger.kernel.org, Matthew Wilcox <matthew@wil.cx>,
dm-devel@redhat.com, linux-fsdevel@vger.kernel.org,
linux-media@vger.kernel.org, Erdem Tumurov <erdemus@gmail.com>,
Vladimir Shelekhov <vshel@iis.nsk.su>
Subject: [PATCH v2] lib/memweight.c: open codes bitmap_weight()
Date: Sat, 24 Aug 2019 13:01:02 +0300 [thread overview]
Message-ID: <20190824100102.1167-1-efremov@ispras.ru> (raw)
In-Reply-To: <20190821074200.2203-1-efremov@ispras.ru>
This patch open codes the bitmap_weight() call. The direct
invocation of hweight_long() allows to remove the BUG_ON and
excessive "longs to bits, bits to longs" conversion.
BUG_ON was required to check that bitmap_weight() will return
a correct value, i.e. the computed weight will fit the int type
of the return value. With this patch memweight() controls the
computation directly with size_t type everywhere. Thus, the BUG_ON
becomes unnecessary.
Total size reduced:
./scripts/bloat-o-meter lib/memweight.o.old lib/memweight.o.new
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10)
Function old new delta
memweight 162 152 -10
Co-developed-by: Erdem Tumurov <erdemus@gmail.com>
Signed-off-by: Erdem Tumurov <erdemus@gmail.com>
Co-developed-by: Vladimir Shelekhov <vshel@iis.nsk.su>
Signed-off-by: Vladimir Shelekhov <vshel@iis.nsk.su>
Signed-off-by: Denis Efremov <efremov@ispras.ru>
---
lib/memweight.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/lib/memweight.c b/lib/memweight.c
index 94dd72ccaa7f..f050b2b4c5e2 100644
--- a/lib/memweight.c
+++ b/lib/memweight.c
@@ -20,11 +20,13 @@ size_t memweight(const void *ptr, size_t bytes)
longs = bytes / sizeof(long);
if (longs) {
- BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
- ret += bitmap_weight((unsigned long *)bitmap,
- longs * BITS_PER_LONG);
+ const unsigned long *bitmap_long =
+ (const unsigned long *)bitmap;
+
bytes -= longs * sizeof(long);
- bitmap += longs * sizeof(long);
+ for (; longs > 0; longs--, bitmap_long++)
+ ret += hweight_long(*bitmap_long);
+ bitmap = (const unsigned char *)bitmap_long;
}
/*
* The reason that this last loop is distinct from the preceding
--
2.21.0
next prev parent reply other threads:[~2019-08-24 10:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 7:42 [PATCH] lib/memweight.c: optimize by inlining bitmap_weight() Denis Efremov
2019-08-22 1:25 ` Andrew Morton
2019-08-22 7:30 ` Denis Efremov
2019-08-24 10:01 ` Denis Efremov [this message]
2019-08-25 6:11 ` [PATCH v2] lib/memweight.c: open codes bitmap_weight() Matthew Wilcox
2019-08-25 11:39 ` Denis Efremov
2019-08-26 18:39 ` Matthew Wilcox
2019-09-13 11:48 ` Denis Efremov
2019-09-13 13:41 ` efremov
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=20190824100102.1167-1-efremov@ispras.ru \
--to=efremov@ispras.ru \
--cc=akinobu.mita@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=dm-devel@redhat.com \
--cc=erdemus@gmail.com \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=matthew@wil.cx \
--cc=vshel@iis.nsk.su \
/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).