From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: Revert "aio: block exit_aio() until all context requests are completed" Date: Fri, 15 May 2015 17:26:48 +0200 Message-ID: <55561038.5080602@de.ibm.com> References: <1431675417-30464-1-git-send-email-borntraeger@de.ibm.com> <5555A33B.20006@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Cc: Gu Zheng , Benjamin LaHaise , linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org To: Jeff Moyer Return-path: In-Reply-To: Sender: stable-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Am 15.05.2015 um 15:42 schrieb Jeff Moyer: > Christian Borntraeger writes: > >> I see a significant latency (can be minutes with 2000 disks and HZ=100) >> when exiting a QEMU process that has lots of disk devices via aio. The >> process sits idle doing nothing as zombie in exit_aio waiting for the >> completion. >> >> Turns out that >> commit 6098b45b32 ("aio: block exit_aio() until all context requests are >> completed") caused the delay. >> >> Patch description was: >> >> It seems that exit_aio() also needs to wait for all iocbs to complete (like >> io_destroy), but we missed the wait step in current implemention, so fix >> it in the same way as we did in io_destroy. >> >> Now: io_destroy requires to block until everything is cleaned up from its >> interface description in the manpage: >> DESCRIPTION >> The io_destroy() system call will attempt to cancel all outstanding >> asynchronous I/O operations against ctx_id, will block on the completion >> of all operations that could not be canceled, and will destroy the ctx_id. >> >> Does process exit require the same full blocking? We might be able to >> cleanup the process and let the aio data structures be freed lazily. >> Opinions or better ideas? > > This has already been fixed: > > commit dc48e56d761610da4ea1088d1bea0a030b8e3e43 > Author: Jens Axboe > Date: Wed Apr 15 11:17:23 2015 -0600 > > aio: fix serial draining in exit_aio() > > Cheers, > Jeff > Cool thanks. As the original patch had cc stable, shouldnt the fix also be backported? Christian