Date: Tue, 24 Oct 2017 02:25:42 +0000 (UTC) From: Warner Losh <imp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r324944 - head/sys/cam Message-ID: <201710240225.v9O2PgnK092044@repo.freebsd.org>
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Author: imp Date: Tue Oct 24 02:25:42 2017 New Revision: 324944 URL: https://svnweb.freebsd.org/changeset/base/324944 Log: Treat a 'current' value of 0 as unlimited as a failsfe. When limiting I/O, a value of 0 makes no sense as a limit. No progress can be made. Trade the possibility that someone might be doing something clever to achieve ultra-low I/O limits vs the damage of not ever making progress on an I/O in favor of making progress. Now the machine won't be useless if this accidentally gets requested. Sponsored by: Netflix Modified: head/sys/cam/cam_iosched.c Modified: head/sys/cam/cam_iosched.c ============================================================================== --- head/sys/cam/cam_iosched.c Tue Oct 24 00:51:11 2017 (r324943) +++ head/sys/cam/cam_iosched.c Tue Oct 24 02:25:42 2017 (r324944) @@ -457,9 +457,10 @@ cam_iosched_iops_caniop(struct iop_stats *ios, struct /* * So if we have any more IOPs left, allow it, - * otherwise wait. + * otherwise wait. If current iops is 0, treat that + * as unlimited as a failsafe. */ - if (ios->l_value1 <= 0) + if (ios->current > 0 && ios->l_value1 <= 0) return EAGAIN; return 0; } @@ -525,8 +526,11 @@ cam_iosched_bw_caniop(struct iop_stats *ios, struct bi * what we let through this quantum (to prevent the * starvation), at the cost of getting a little less * next quantum. + * + * Also note that if the current limit is <= 0, + * we treat it as unlimited as a failsafe. */ - if (ios->l_value1 <= 0) + if (ios->current > 0 && ios->l_value1 <= 0) return EAGAIN;
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