From patchwork Tue Oct 11 19:04:52 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Wheeler X-Patchwork-Id: 9819175 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 9DE37603D7 for ; Fri, 30 Jun 2017 10:22:03 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8F7342856E for ; Fri, 30 Jun 2017 10:22:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 843582861A; Fri, 30 Jun 2017 10:22:03 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=2.0 tests=BAYES_00, DATE_IN_PAST_96_XX, RCVD_IN_DNSWL_HI,RCVD_IN_SORBS_SPAM autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A2EB428639 for ; Fri, 30 Jun 2017 10:22:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752453AbdF3KVm (ORCPT ); Fri, 30 Jun 2017 06:21:42 -0400 Received: from iad1-shared-relay2.dreamhost.com ([208.113.157.41]:45174 "EHLO iad1-shared-relay2.dreamhost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752448AbdF3KVU (ORCPT ); Fri, 30 Jun 2017 06:21:20 -0400 Received: from iad1-shared-relay1.dreamhost.com (iad1-shared-relay1.dreamhost.com [208.113.157.50]) by iad1-shared-relay2.dreamhost.com (Postfix) with ESMTP id C227B3E5682 for ; Thu, 29 Jun 2017 15:21:08 -0700 (PDT) Received: from ware.dreamhost.com (ware.dreamhost.com [64.111.127.160]) by iad1-shared-relay1.dreamhost.com (Postfix) with ESMTP id 17A88B400B0 for ; Thu, 29 Jun 2017 15:21:08 -0700 (PDT) Received: by ware.dreamhost.com (Postfix, from userid 2406546) id EB4EA100130; Thu, 29 Jun 2017 15:21:07 -0700 (PDT) In-Reply-To: <20170629134510.GA32385@infradead.org> References: <20170629134510.GA32385@infradead.org> From: Eric Wheeler Date: Tue, 11 Oct 2016 12:04:52 -0700 Subject: [PATCH 07/19] bcache: introduce bcache sysfs entries for ioprio-based bypass/writeback hints To: linux-block@vger.kernel.org Message-Id: <20170629222107.EB4EA100130@ware.dreamhost.com> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add sysfs entries to support to hint for bypass/writeback by the ioprio assigned to the bio. If the bio is unassigned, use current's io-context ioprio for cache writeback or bypass (configured per-process with `ionice`). Having idle IOs bypass the cache can increase performance elsewhere since you probably don't care about their performance. In addition, this prevents idle IOs from promoting into (polluting) your cache and evicting blocks that are more important elsewhere. If you really nead the performance at the expense of SSD wearout, then configure ioprio_writeback and set your `ionice` appropriately. For example: echo 2,7 > /sys/block/bcache0/bcache/ioprio_bypass echo 2,0 > /sys/block/bcache0/bcache/ioprio_writeback See the documentation commit for details. Signed-off-by: Eric Wheeler Acked-by: Kent Overstreet Tested-by: Kai Krakow Cc: nix@esperi.org.uk --- drivers/md/bcache/bcache.h | 3 ++ drivers/md/bcache/request.c | 24 +++++++++++++++ drivers/md/bcache/sysfs.c | 71 +++++++++++++++++++++++++++++++++++++++++++ drivers/md/bcache/writeback.c | 8 +++++ drivers/md/bcache/writeback.h | 24 +++++++++++++++ 5 files changed, 130 insertions(+) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index dee542f..44123e4 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -367,6 +367,9 @@ struct cached_dev { unsigned writeback_rate_update_seconds; unsigned writeback_rate_d_term; unsigned writeback_rate_p_term_inverse; + + unsigned short ioprio_writeback; + unsigned short ioprio_bypass; }; enum alloc_reserve { diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index d27707d..a95609f 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -373,6 +373,8 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio) unsigned sectors, congested = bch_get_congested(c); struct task_struct *task = current; struct io *i; + struct io_context *ioc; + unsigned short ioprio; if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) || c->gc_stats.in_use > CUTOFF_CACHE_ADD || @@ -384,6 +386,28 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio) op_is_write(bio_op(bio)))) goto skip; + /* If the ioprio already exists on the bio, use that. We assume that + * the upper layer properly assigned the calling process's ioprio to + * the bio being passed to bcache. Otherwise, use current's ioc. */ + ioprio = bio_prio(bio); + if (!ioprio_valid(ioprio)) { + ioc = get_task_io_context(current, GFP_NOIO, NUMA_NO_NODE); + if (ioc) { + if (ioprio_valid(ioc->ioprio)) + ioprio = ioc->ioprio; + put_io_context(ioc); + ioc = NULL; + } + } + + /* If process ioprio is lower-or-equal to dc->ioprio_bypass, then + * hint for bypass. Note that a lower-priority IO class+value + * has a greater numeric value. */ + if (ioprio_valid(ioprio) && ioprio_valid(dc->ioprio_writeback) + && ioprio >= dc->ioprio_bypass) { + return true; + } + if (bio->bi_iter.bi_sector & (c->sb.block_size - 1) || bio_sectors(bio) & (c->sb.block_size - 1)) { pr_debug("skipping unaligned io"); diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index f90f136..cc0076d 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -107,6 +107,9 @@ rw_attribute(btree_shrinker_disabled); rw_attribute(copy_gc_enabled); rw_attribute(size); +rw_attribute(ioprio_writeback); +rw_attribute(ioprio_bypass); + SHOW(__bch_cached_dev) { struct cached_dev *dc = container_of(kobj, struct cached_dev, @@ -183,6 +186,17 @@ SHOW(__bch_cached_dev) return strlen(buf); } + if (attr == &sysfs_ioprio_bypass) + return snprintf(buf, PAGE_SIZE-1, "%d,%ld\n", + IOPRIO_PRIO_CLASS(dc->ioprio_bypass), + IOPRIO_PRIO_DATA(dc->ioprio_bypass)); + + if (attr == &sysfs_ioprio_writeback) + return snprintf(buf, PAGE_SIZE-1, "%d,%ld\n", + IOPRIO_PRIO_CLASS(dc->ioprio_writeback), + IOPRIO_PRIO_DATA(dc->ioprio_writeback)); + + #undef var return 0; } @@ -195,6 +209,10 @@ STORE(__cached_dev) unsigned v = size; struct cache_set *c; struct kobj_uevent_env *env; + unsigned ioprio_class = 0; /* invalid initial ioprio values */ + unsigned ioprio_level = IOPRIO_BE_NR; + unsigned short *ioprio_hint = NULL; + char *ioprio_type = NULL; #define d_strtoul(var) sysfs_strtoul(var, dc->var) #define d_strtoul_nonzero(var) sysfs_strtoul_clamp(var, dc->var, 1, INT_MAX) @@ -283,6 +301,57 @@ STORE(__cached_dev) if (attr == &sysfs_stop) bcache_device_stop(&dc->disk); + /* ioprio hinting: we use ioprio_hint to reduce duplicate printk verbiage */ + if (attr == &sysfs_ioprio_writeback) { + ioprio_hint = &dc->ioprio_writeback; + ioprio_type = "writeback"; + } + + if (attr == &sysfs_ioprio_bypass) { + ioprio_hint = &dc->ioprio_bypass; + ioprio_type = "bypass"; + } + + if (ioprio_hint != NULL) + { + if (sscanf(buf, "%u,%u", &ioprio_class, &ioprio_level) != 2 + || ioprio_class > IOPRIO_CLASS_IDLE + || ioprio_level >= IOPRIO_BE_NR) { + pr_err("ioprio_%s invalid, expecting: (class,level) but parsed (%u,%u); ignored.", + ioprio_type, + ioprio_class, ioprio_level); + return size; + } + + /* Use the maximum(/minimum) value in the class shift space to make integer + comparison correct for ioprio_writeback(/ioprio_bypass) for IOPRIO_CLASS_IDLE. + This is necessary because there are no ioprio levels for the idle class. */ + if (ioprio_class == IOPRIO_CLASS_IDLE) { + if (ioprio_hint == &dc->ioprio_writeback) + ioprio_level = IOPRIO_PRIO_MASK; + else + /* Same, but 0 for bypass (inverted vs. writeback) */ + ioprio_level = 0; + } + + *ioprio_hint = IOPRIO_PRIO_VALUE(ioprio_class, ioprio_level); + + if (!ioprio_valid(*ioprio_hint)) + pr_info("disabled ioprio_%s hints.", ioprio_type); + else + pr_info("set hint for cache %s with priority %s: (class,level) = (%u,%u)", + ioprio_type, + ( ioprio_hint == &dc->ioprio_writeback ? "at-or-above" : "at-or-below" ), + ioprio_class, ioprio_level); + + if (ioprio_valid(dc->ioprio_writeback) + && ioprio_valid(dc->ioprio_bypass) + && dc->ioprio_writeback >= dc->ioprio_bypass) + pr_warning( + "warning: ioprio_writeback hint is neither disabled nor higher priority than the bypass hint; " + "will always writeback!"); + } + return size; } @@ -335,6 +404,8 @@ static struct attribute *bch_cached_dev_files[] = { &sysfs_verify, &sysfs_bypass_torture_test, #endif + &sysfs_ioprio_bypass, + &sysfs_ioprio_writeback, NULL }; KTYPE(bch_cached_dev); diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index 42c66e7..3d463f0 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -511,6 +511,14 @@ void bch_cached_dev_writeback_init(struct cached_dev *dc) dc->writeback_rate_d_term = 30; dc->writeback_rate_p_term_inverse = 6000; + /* These defaults provide the best SSD life by enabling bypass + for priorities at-or-below BE-7. This also provides better + performance (cache hits) by preventing (near-)idle processes from + polluting the cache working set. Only set ioprio_writeback if + you really need it: it will wear out your SSD sooner. */ + dc->ioprio_writeback = IOPRIO_PRIO_VALUE(0, 0); + dc->ioprio_bypass = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, (IOPRIO_BE_NR-1)); + INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); } diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h index 629bd1a..cd82fe8 100644 --- a/drivers/md/bcache/writeback.h +++ b/drivers/md/bcache/writeback.h @@ -43,6 +43,8 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio, unsigned cache_mode, bool would_skip) { unsigned in_use = dc->disk.c->gc_stats.in_use; + struct io_context *ioc; + unsigned short ioprio; if (cache_mode != CACHE_MODE_WRITEBACK || test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) || @@ -57,6 +59,28 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio, if (would_skip) return false; + /* If the ioprio already exists on the bio, use that. We assume that + * the upper layer properly assigned the calling process's ioprio to + * the bio being passed to bcache. Otherwise, use current's ioc. */ + ioprio = bio_prio(bio); + if (!ioprio_valid(ioprio)) { + ioc = get_task_io_context(current, GFP_NOIO, NUMA_NO_NODE); + if (ioc) { + if (ioprio_valid(ioc->ioprio)) + ioprio = ioc->ioprio; + put_io_context(ioc); + ioc = NULL; + } + } + + /* If process ioprio is higher-or-equal to dc->ioprio_writeback, then + * hint for writeback. Note that a higher-priority IO class+value + * has a lesser numeric value. */ + if (ioprio_valid(ioprio) && ioprio_valid(dc->ioprio_writeback) + && ioprio <= dc->ioprio_writeback) { + return true; + } + return op_is_sync(bio->bi_opf) || in_use <= CUTOFF_WRITEBACK; }