From: Hui Tang <tanghui20@huawei.com>
To: Russell King <linux@armlinux.org.uk>
Cc: <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, Jens Axboe <axboe@kernel.dk>,
<tanghui20@huawei.com>
Subject: [bug-report] possible performance problem in ret_to_user_from_irq
Date: Mon, 26 Dec 2022 16:45:20 +0800 [thread overview]
Message-ID: <7ecb8f3c-2aeb-a905-0d4a-aa768b9649b5@huawei.com> (raw)
hi folks.
I found a performance problem which is introduced by commit
32d59773da38 ("arm: add support for TIF_NOTIFY_SIGNAL").
After the commit, any bit in the range of 0..15 will cause
do_work_pending() to be invoked. More frequent do_work_pending()
invoked possible result in worse performance.
Some of the tests I've done， as follows:
lmbench test base with patch
./lat_ctx -P 1 -s 0 2 7.3167 11.04
./lat_ctx -P 1 -s 16 2 8.0467 14.5367
./lat_ctx -P 1 -s 64 2 7.8667 11.43
./lat_ctx -P 1 -s 16 16 16.47 18.3667
./lat_pipe -P 1 28.1671 44.7904
libMicro-0.4.1 test base with patch
./cascade_cond -E -C 200\
-L -S -W -N "c_cond_1" -I 100 286.3333 358
When I adjust test bit, the performance problem gone.
- movs r1, r1, lsl #16
+ ldr r2, =#_TIF_WORK_MASK
+ tst r1, r2
Does anyone have a good suggestion for this problem?
should just test _TIF_WORK_MASK, as before?
next reply other threads:[~2022-12-26 8:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-26 8:45 Hui Tang [this message]
2023-01-03 10:06 ` [bug-report] possible performance problem in ret_to_user_from_irq Russell King (Oracle)
2023-01-03 14:25 ` Jens Axboe
2023-01-03 14:34 ` Russell King (Oracle)
2023-01-03 14:59 ` Jens Axboe
2023-01-04 1:31 ` Hui Tang
2023-01-04 7:04 ` Hui Tang
2023-01-04 14:45 ` Jens Axboe
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