From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753088Ab3F2RtJ (ORCPT ); Sat, 29 Jun 2013 13:49:09 -0400 Received: from relay.parallels.com ([195.214.232.42]:52185 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752152Ab3F2RtE (ORCPT ); Sat, 29 Jun 2013 13:49:04 -0400 Subject: [PATCH 16/16] mm: strictlimit feature To: miklos@szeredi.hu From: Maxim Patlasov Cc: riel@redhat.com, dev@parallels.com, xemul@parallels.com, fuse-devel@lists.sourceforge.net, bfoster@redhat.com, linux-kernel@vger.kernel.org, jbottomley@parallels.com, linux-mm@kvack.org, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org, fengguang.wu@intel.com, devel@openvz.org, mgorman@suse.de Date: Sat, 29 Jun 2013 21:48:54 +0400 Message-ID: <20130629174706.20175.78184.stgit@maximpc.sw.ru> In-Reply-To: <20130629172211.20175.70154.stgit@maximpc.sw.ru> References: <20130629172211.20175.70154.stgit@maximpc.sw.ru> User-Agent: StGit/0.15 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Miklos Szeredi The feature prevents mistrusted filesystems to grow a large number of dirty pages before throttling. For such filesystems balance_dirty_pages always check bdi counters against bdi limits. I.e. even if global "nr_dirty" is under "freerun", it's not allowed to skip bdi checks. The only use case for now is fuse: it sets bdi max_ratio to 1% by default and system administrators are supposed to expect that this limit won't be exceeded. The feature is on if address space is marked by AS_STRICTLIMIT flag. A filesystem may set the flag when it initializes a new inode. Signed-off-by: Maxim Patlasov --- fs/fs-writeback.c | 2 - fs/fuse/file.c | 3 + fs/fuse/inode.c | 1 include/linux/backing-dev.h | 5 ++ include/linux/pagemap.h | 1 include/linux/writeback.h | 3 + mm/backing-dev.c | 3 + mm/page-writeback.c | 131 +++++++++++++++++++++++++++++++++---------- 8 files changed, 116 insertions(+), 33 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 3be5718..8c75277 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -762,7 +762,7 @@ static bool over_bground_thresh(struct backing_dev_info *bdi) static void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time) { - __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time); + __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time, false); } /* diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 6d30db1..99b5c97 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1697,6 +1697,7 @@ static int fuse_writepage_locked(struct page *page, req->inode = inode; inc_bdi_stat(mapping->backing_dev_info, BDI_WRITEBACK); + inc_bdi_stat(mapping->backing_dev_info, BDI_WRITTEN_BACK); inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP); end_page_writeback(page); @@ -1766,6 +1767,7 @@ static int fuse_send_writepages(struct fuse_fill_wb_data *data) if (tmp_page) { copy_highpage(tmp_page, page); inc_bdi_stat(bdi, BDI_WRITEBACK); + inc_bdi_stat(bdi, BDI_WRITTEN_BACK); inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP); } else all_ok = 0; @@ -1781,6 +1783,7 @@ static int fuse_send_writepages(struct fuse_fill_wb_data *data) struct page *page = req->pages[i]; if (page) { dec_bdi_stat(bdi, BDI_WRITEBACK); + dec_bdi_stat(bdi, BDI_WRITTEN_BACK); dec_zone_page_state(page, NR_WRITEBACK_TEMP); __free_page(page); req->pages[i] = NULL; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 4beb8e3..00a28af 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -305,6 +305,7 @@ struct inode *fuse_iget(struct super_block *sb, u64 nodeid, inode->i_flags |= S_NOCMTIME; inode->i_generation = generation; inode->i_data.backing_dev_info = &fc->bdi; + set_bit(AS_STRICTLIMIT, &inode->i_data.flags); fuse_init_inode(inode, attr); unlock_new_inode(inode); } else if ((inode->i_mode ^ attr->mode) & S_IFMT) { diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index c388155..9c368af 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -33,6 +33,8 @@ enum bdi_state { BDI_sync_congested, /* The sync queue is getting full */ BDI_registered, /* bdi_register() was done */ BDI_writeback_running, /* Writeback is in progress */ + BDI_idle, /* No pages under writeback at the moment of + * last update of write bw */ BDI_unused, /* Available bits start here */ }; @@ -43,6 +45,7 @@ enum bdi_stat_item { BDI_WRITEBACK, BDI_DIRTIED, BDI_WRITTEN, + BDI_WRITTEN_BACK, NR_BDI_STAT_ITEMS }; @@ -76,6 +79,8 @@ struct backing_dev_info { unsigned long bw_time_stamp; /* last time write bw is updated */ unsigned long dirtied_stamp; unsigned long written_stamp; /* pages written at bw_time_stamp */ + unsigned long writeback_stamp; /* pages sent to writeback at + * bw_time_stamp */ unsigned long write_bandwidth; /* the estimated write bandwidth */ unsigned long avg_write_bandwidth; /* further smoothed write bw */ diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index e3dea75..baac702 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -25,6 +25,7 @@ enum mapping_flags { AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */ AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */ AS_BALLOON_MAP = __GFP_BITS_SHIFT + 4, /* balloon page special map */ + AS_STRICTLIMIT = __GFP_BITS_SHIFT + 5, /* strict dirty limit */ }; static inline void mapping_set_error(struct address_space *mapping, int error) diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 579a500..5144051 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -159,7 +159,8 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, - unsigned long start_time); + unsigned long start_time, + bool strictlimit); void page_writeback_init(void); void balance_dirty_pages_ratelimited(struct address_space *mapping); diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 5025174..71413d6 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -94,6 +94,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) "BackgroundThresh: %10lu kB\n" "BdiDirtied: %10lu kB\n" "BdiWritten: %10lu kB\n" + "BdiWrittenBack: %10lu kB\n" "BdiWriteBandwidth: %10lu kBps\n" "b_dirty: %10lu\n" "b_io: %10lu\n" @@ -107,6 +108,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) K(background_thresh), (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)), (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)), + (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN_BACK)), (unsigned long) K(bdi->write_bandwidth), nr_dirty, nr_io, @@ -455,6 +457,7 @@ int bdi_init(struct backing_dev_info *bdi) bdi->bw_time_stamp = jiffies; bdi->written_stamp = 0; + bdi->writeback_stamp = 0; bdi->balanced_dirty_ratelimit = INIT_BW; bdi->dirty_ratelimit = INIT_BW; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 4514ad7..77449b0 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -585,6 +585,37 @@ unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) } /* + * setpoint - dirty 3 + * f(dirty) := 1.0 + (----------------) + * limit - setpoint + * + * it's a 3rd order polynomial that subjects to + * + * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast + * (2) f(setpoint) = 1.0 => the balance point + * (3) f(limit) = 0 => the hard limit + * (4) df/dx <= 0 => negative feedback control + * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) + * => fast response on large errors; small oscillation near setpoint + */ +static inline long long pos_ratio_polynom(unsigned long setpoint, + unsigned long dirty, + unsigned long limit) +{ + long long pos_ratio; + long x; + + x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, + limit - setpoint + 1); + pos_ratio = x; + pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; + pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; + pos_ratio += 1 << RATELIMIT_CALC_SHIFT; + + return pos_ratio; +} + +/* * Dirty position control. * * (o) global/bdi setpoints @@ -664,7 +695,8 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, unsigned long bg_thresh, unsigned long dirty, unsigned long bdi_thresh, - unsigned long bdi_dirty) + unsigned long bdi_dirty, + bool strictlimit) { unsigned long write_bw = bdi->avg_write_bandwidth; unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); @@ -679,29 +711,31 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, if (unlikely(dirty >= limit)) return 0; + if (unlikely(strictlimit)) { + if (bdi_dirty < 8) + return 2 << RATELIMIT_CALC_SHIFT; + + if (bdi_dirty >= bdi_thresh) + return 0; + + bdi_setpoint = bdi_thresh + bdi_dirty_limit(bdi, bg_thresh); + bdi_setpoint /= 2; + + if (bdi_setpoint == 0 || bdi_setpoint == bdi_thresh) + return 0; + + pos_ratio = pos_ratio_polynom(bdi_setpoint, bdi_dirty, + bdi_thresh); + return min_t(long long, pos_ratio, 2 << RATELIMIT_CALC_SHIFT); + } + /* * global setpoint * - * setpoint - dirty 3 - * f(dirty) := 1.0 + (----------------) - * limit - setpoint - * - * it's a 3rd order polynomial that subjects to - * - * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast - * (2) f(setpoint) = 1.0 => the balance point - * (3) f(limit) = 0 => the hard limit - * (4) df/dx <= 0 => negative feedback control - * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) - * => fast response on large errors; small oscillation near setpoint + * See comment for pos_ratio_polynom(). */ setpoint = (freerun + limit) / 2; - x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, - limit - setpoint + 1); - pos_ratio = x; - pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; - pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; - pos_ratio += 1 << RATELIMIT_CALC_SHIFT; + pos_ratio = pos_ratio_polynom(setpoint, dirty, limit); /* * We have computed basic pos_ratio above based on global situation. If @@ -892,7 +926,8 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, unsigned long bdi_thresh, unsigned long bdi_dirty, unsigned long dirtied, - unsigned long elapsed) + unsigned long elapsed, + bool strictlimit) { unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); unsigned long limit = hard_dirty_limit(thresh); @@ -913,7 +948,7 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty); + bdi_thresh, bdi_dirty, strictlimit); /* * task_ratelimit reflects each dd's dirty rate for the past 200ms. */ @@ -994,6 +1029,16 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, * keep that period small to reduce time lags). */ step = 0; + + if (unlikely(strictlimit)) { + dirty = bdi_dirty; + if (bdi_dirty < 8) + setpoint = bdi_dirty + 1; + else + setpoint = (bdi_thresh + + bdi_dirty_limit(bdi, bg_thresh)) / 2; + } + if (dirty < setpoint) { x = min(bdi->balanced_dirty_ratelimit, min(balanced_dirty_ratelimit, task_ratelimit)); @@ -1034,12 +1079,14 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, - unsigned long start_time) + unsigned long start_time, + bool strictlimit) { unsigned long now = jiffies; unsigned long elapsed = now - bdi->bw_time_stamp; unsigned long dirtied; unsigned long written; + unsigned long writeback; /* * rate-limit, only update once every 200ms. @@ -1049,6 +1096,7 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); + writeback = bdi_stat_sum(bdi, BDI_WRITTEN_BACK); /* * Skip quiet periods when disk bandwidth is under-utilized. @@ -1057,11 +1105,15 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) goto snapshot; + if (test_bit(BDI_idle, &bdi->state) && + bdi->writeback_stamp == writeback) + goto snapshot; + if (thresh) { global_update_bandwidth(thresh, dirty, now); bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty, - dirtied, elapsed); + dirtied, elapsed, strictlimit); } bdi_update_write_bandwidth(bdi, elapsed, written); @@ -1069,6 +1121,12 @@ snapshot: bdi->dirtied_stamp = dirtied; bdi->written_stamp = written; bdi->bw_time_stamp = now; + + bdi->writeback_stamp = writeback; + if (bdi_stat_sum(bdi, BDI_WRITEBACK) == 0) + set_bit(BDI_idle, &bdi->state); + else + clear_bit(BDI_idle, &bdi->state); } static void bdi_update_bandwidth(struct backing_dev_info *bdi, @@ -1077,13 +1135,14 @@ static void bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, - unsigned long start_time) + unsigned long start_time, + bool strictlimit) { if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) return; spin_lock(&bdi->wb.list_lock); __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty, start_time); + bdi_thresh, bdi_dirty, start_time, strictlimit); spin_unlock(&bdi->wb.list_lock); } @@ -1226,6 +1285,7 @@ static void balance_dirty_pages(struct address_space *mapping, unsigned long dirty_ratelimit; unsigned long pos_ratio; struct backing_dev_info *bdi = mapping->backing_dev_info; + bool strictlimit = test_bit(AS_STRICTLIMIT, &mapping->flags); unsigned long start_time = jiffies; for (;;) { @@ -1250,7 +1310,7 @@ static void balance_dirty_pages(struct address_space *mapping, */ freerun = dirty_freerun_ceiling(dirty_thresh, background_thresh); - if (nr_dirty <= freerun) { + if (nr_dirty <= freerun && !strictlimit) { current->dirty_paused_when = now; current->nr_dirtied = 0; current->nr_dirtied_pause = @@ -1258,7 +1318,7 @@ static void balance_dirty_pages(struct address_space *mapping, break; } - if (unlikely(!writeback_in_progress(bdi))) + if (unlikely(!writeback_in_progress(bdi)) && !strictlimit) bdi_start_background_writeback(bdi); /* @@ -1296,19 +1356,24 @@ static void balance_dirty_pages(struct address_space *mapping, bdi_stat(bdi, BDI_WRITEBACK); } + if (unlikely(!writeback_in_progress(bdi)) && + bdi_dirty > bdi_thresh / 4) + bdi_start_background_writeback(bdi); + dirty_exceeded = (bdi_dirty > bdi_thresh) && - (nr_dirty > dirty_thresh); + ((nr_dirty > dirty_thresh) || strictlimit); if (dirty_exceeded && !bdi->dirty_exceeded) bdi->dirty_exceeded = 1; bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty, - start_time); + start_time, strictlimit); dirty_ratelimit = bdi->dirty_ratelimit; pos_ratio = bdi_position_ratio(bdi, dirty_thresh, background_thresh, nr_dirty, - bdi_thresh, bdi_dirty); + bdi_thresh, bdi_dirty, + strictlimit); task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> RATELIMIT_CALC_SHIFT; max_pause = bdi_max_pause(bdi, bdi_dirty); @@ -1362,6 +1427,8 @@ static void balance_dirty_pages(struct address_space *mapping, } pause: + if (unlikely(!writeback_in_progress(bdi))) + bdi_start_background_writeback(bdi); trace_balance_dirty_pages(bdi, dirty_thresh, background_thresh, @@ -2265,8 +2332,10 @@ int test_set_page_writeback(struct page *page) radix_tree_tag_set(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); - if (bdi_cap_account_writeback(bdi)) + if (bdi_cap_account_writeback(bdi)) { __inc_bdi_stat(bdi, BDI_WRITEBACK); + __inc_bdi_stat(bdi, BDI_WRITTEN_BACK); + } } if (!PageDirty(page)) radix_tree_tag_clear(&mapping->page_tree, From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx153.postini.com [74.125.245.153]) by kanga.kvack.org (Postfix) with SMTP id 1BF746B0036 for ; Sat, 29 Jun 2013 13:49:08 -0400 (EDT) Subject: [PATCH 16/16] mm: strictlimit feature From: Maxim Patlasov Date: Sat, 29 Jun 2013 21:48:54 +0400 Message-ID: <20130629174706.20175.78184.stgit@maximpc.sw.ru> In-Reply-To: <20130629172211.20175.70154.stgit@maximpc.sw.ru> References: <20130629172211.20175.70154.stgit@maximpc.sw.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: miklos@szeredi.hu Cc: riel@redhat.com, dev@parallels.com, xemul@parallels.com, fuse-devel@lists.sourceforge.net, bfoster@redhat.com, linux-kernel@vger.kernel.org, jbottomley@parallels.com, linux-mm@kvack.org, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org, fengguang.wu@intel.com, devel@openvz.org, mgorman@suse.de From: Miklos Szeredi The feature prevents mistrusted filesystems to grow a large number of dirty pages before throttling. For such filesystems balance_dirty_pages always check bdi counters against bdi limits. I.e. even if global "nr_dirty" is under "freerun", it's not allowed to skip bdi checks. The only use case for now is fuse: it sets bdi max_ratio to 1% by default and system administrators are supposed to expect that this limit won't be exceeded. The feature is on if address space is marked by AS_STRICTLIMIT flag. A filesystem may set the flag when it initializes a new inode. Signed-off-by: Maxim Patlasov --- fs/fs-writeback.c | 2 - fs/fuse/file.c | 3 + fs/fuse/inode.c | 1 include/linux/backing-dev.h | 5 ++ include/linux/pagemap.h | 1 include/linux/writeback.h | 3 + mm/backing-dev.c | 3 + mm/page-writeback.c | 131 +++++++++++++++++++++++++++++++++---------- 8 files changed, 116 insertions(+), 33 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 3be5718..8c75277 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -762,7 +762,7 @@ static bool over_bground_thresh(struct backing_dev_info *bdi) static void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time) { - __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time); + __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time, false); } /* diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 6d30db1..99b5c97 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1697,6 +1697,7 @@ static int fuse_writepage_locked(struct page *page, req->inode = inode; inc_bdi_stat(mapping->backing_dev_info, BDI_WRITEBACK); + inc_bdi_stat(mapping->backing_dev_info, BDI_WRITTEN_BACK); inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP); end_page_writeback(page); @@ -1766,6 +1767,7 @@ static int fuse_send_writepages(struct fuse_fill_wb_data *data) if (tmp_page) { copy_highpage(tmp_page, page); inc_bdi_stat(bdi, BDI_WRITEBACK); + inc_bdi_stat(bdi, BDI_WRITTEN_BACK); inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP); } else all_ok = 0; @@ -1781,6 +1783,7 @@ static int fuse_send_writepages(struct fuse_fill_wb_data *data) struct page *page = req->pages[i]; if (page) { dec_bdi_stat(bdi, BDI_WRITEBACK); + dec_bdi_stat(bdi, BDI_WRITTEN_BACK); dec_zone_page_state(page, NR_WRITEBACK_TEMP); __free_page(page); req->pages[i] = NULL; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 4beb8e3..00a28af 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -305,6 +305,7 @@ struct inode *fuse_iget(struct super_block *sb, u64 nodeid, inode->i_flags |= S_NOCMTIME; inode->i_generation = generation; inode->i_data.backing_dev_info = &fc->bdi; + set_bit(AS_STRICTLIMIT, &inode->i_data.flags); fuse_init_inode(inode, attr); unlock_new_inode(inode); } else if ((inode->i_mode ^ attr->mode) & S_IFMT) { diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index c388155..9c368af 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -33,6 +33,8 @@ enum bdi_state { BDI_sync_congested, /* The sync queue is getting full */ BDI_registered, /* bdi_register() was done */ BDI_writeback_running, /* Writeback is in progress */ + BDI_idle, /* No pages under writeback at the moment of + * last update of write bw */ BDI_unused, /* Available bits start here */ }; @@ -43,6 +45,7 @@ enum bdi_stat_item { BDI_WRITEBACK, BDI_DIRTIED, BDI_WRITTEN, + BDI_WRITTEN_BACK, NR_BDI_STAT_ITEMS }; @@ -76,6 +79,8 @@ struct backing_dev_info { unsigned long bw_time_stamp; /* last time write bw is updated */ unsigned long dirtied_stamp; unsigned long written_stamp; /* pages written at bw_time_stamp */ + unsigned long writeback_stamp; /* pages sent to writeback at + * bw_time_stamp */ unsigned long write_bandwidth; /* the estimated write bandwidth */ unsigned long avg_write_bandwidth; /* further smoothed write bw */ diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index e3dea75..baac702 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -25,6 +25,7 @@ enum mapping_flags { AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */ AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */ AS_BALLOON_MAP = __GFP_BITS_SHIFT + 4, /* balloon page special map */ + AS_STRICTLIMIT = __GFP_BITS_SHIFT + 5, /* strict dirty limit */ }; static inline void mapping_set_error(struct address_space *mapping, int error) diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 579a500..5144051 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -159,7 +159,8 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, - unsigned long start_time); + unsigned long start_time, + bool strictlimit); void page_writeback_init(void); void balance_dirty_pages_ratelimited(struct address_space *mapping); diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 5025174..71413d6 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -94,6 +94,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) "BackgroundThresh: %10lu kB\n" "BdiDirtied: %10lu kB\n" "BdiWritten: %10lu kB\n" + "BdiWrittenBack: %10lu kB\n" "BdiWriteBandwidth: %10lu kBps\n" "b_dirty: %10lu\n" "b_io: %10lu\n" @@ -107,6 +108,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) K(background_thresh), (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)), (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)), + (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN_BACK)), (unsigned long) K(bdi->write_bandwidth), nr_dirty, nr_io, @@ -455,6 +457,7 @@ int bdi_init(struct backing_dev_info *bdi) bdi->bw_time_stamp = jiffies; bdi->written_stamp = 0; + bdi->writeback_stamp = 0; bdi->balanced_dirty_ratelimit = INIT_BW; bdi->dirty_ratelimit = INIT_BW; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 4514ad7..77449b0 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -585,6 +585,37 @@ unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty) } /* + * setpoint - dirty 3 + * f(dirty) := 1.0 + (----------------) + * limit - setpoint + * + * it's a 3rd order polynomial that subjects to + * + * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast + * (2) f(setpoint) = 1.0 => the balance point + * (3) f(limit) = 0 => the hard limit + * (4) df/dx <= 0 => negative feedback control + * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) + * => fast response on large errors; small oscillation near setpoint + */ +static inline long long pos_ratio_polynom(unsigned long setpoint, + unsigned long dirty, + unsigned long limit) +{ + long long pos_ratio; + long x; + + x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, + limit - setpoint + 1); + pos_ratio = x; + pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; + pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; + pos_ratio += 1 << RATELIMIT_CALC_SHIFT; + + return pos_ratio; +} + +/* * Dirty position control. * * (o) global/bdi setpoints @@ -664,7 +695,8 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, unsigned long bg_thresh, unsigned long dirty, unsigned long bdi_thresh, - unsigned long bdi_dirty) + unsigned long bdi_dirty, + bool strictlimit) { unsigned long write_bw = bdi->avg_write_bandwidth; unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); @@ -679,29 +711,31 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, if (unlikely(dirty >= limit)) return 0; + if (unlikely(strictlimit)) { + if (bdi_dirty < 8) + return 2 << RATELIMIT_CALC_SHIFT; + + if (bdi_dirty >= bdi_thresh) + return 0; + + bdi_setpoint = bdi_thresh + bdi_dirty_limit(bdi, bg_thresh); + bdi_setpoint /= 2; + + if (bdi_setpoint == 0 || bdi_setpoint == bdi_thresh) + return 0; + + pos_ratio = pos_ratio_polynom(bdi_setpoint, bdi_dirty, + bdi_thresh); + return min_t(long long, pos_ratio, 2 << RATELIMIT_CALC_SHIFT); + } + /* * global setpoint * - * setpoint - dirty 3 - * f(dirty) := 1.0 + (----------------) - * limit - setpoint - * - * it's a 3rd order polynomial that subjects to - * - * (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast - * (2) f(setpoint) = 1.0 => the balance point - * (3) f(limit) = 0 => the hard limit - * (4) df/dx <= 0 => negative feedback control - * (5) the closer to setpoint, the smaller |df/dx| (and the reverse) - * => fast response on large errors; small oscillation near setpoint + * See comment for pos_ratio_polynom(). */ setpoint = (freerun + limit) / 2; - x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, - limit - setpoint + 1); - pos_ratio = x; - pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; - pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; - pos_ratio += 1 << RATELIMIT_CALC_SHIFT; + pos_ratio = pos_ratio_polynom(setpoint, dirty, limit); /* * We have computed basic pos_ratio above based on global situation. If @@ -892,7 +926,8 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, unsigned long bdi_thresh, unsigned long bdi_dirty, unsigned long dirtied, - unsigned long elapsed) + unsigned long elapsed, + bool strictlimit) { unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); unsigned long limit = hard_dirty_limit(thresh); @@ -913,7 +948,7 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed; pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty); + bdi_thresh, bdi_dirty, strictlimit); /* * task_ratelimit reflects each dd's dirty rate for the past 200ms. */ @@ -994,6 +1029,16 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, * keep that period small to reduce time lags). */ step = 0; + + if (unlikely(strictlimit)) { + dirty = bdi_dirty; + if (bdi_dirty < 8) + setpoint = bdi_dirty + 1; + else + setpoint = (bdi_thresh + + bdi_dirty_limit(bdi, bg_thresh)) / 2; + } + if (dirty < setpoint) { x = min(bdi->balanced_dirty_ratelimit, min(balanced_dirty_ratelimit, task_ratelimit)); @@ -1034,12 +1079,14 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, - unsigned long start_time) + unsigned long start_time, + bool strictlimit) { unsigned long now = jiffies; unsigned long elapsed = now - bdi->bw_time_stamp; unsigned long dirtied; unsigned long written; + unsigned long writeback; /* * rate-limit, only update once every 200ms. @@ -1049,6 +1096,7 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]); written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]); + writeback = bdi_stat_sum(bdi, BDI_WRITTEN_BACK); /* * Skip quiet periods when disk bandwidth is under-utilized. @@ -1057,11 +1105,15 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi, if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time)) goto snapshot; + if (test_bit(BDI_idle, &bdi->state) && + bdi->writeback_stamp == writeback) + goto snapshot; + if (thresh) { global_update_bandwidth(thresh, dirty, now); bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty, - dirtied, elapsed); + dirtied, elapsed, strictlimit); } bdi_update_write_bandwidth(bdi, elapsed, written); @@ -1069,6 +1121,12 @@ snapshot: bdi->dirtied_stamp = dirtied; bdi->written_stamp = written; bdi->bw_time_stamp = now; + + bdi->writeback_stamp = writeback; + if (bdi_stat_sum(bdi, BDI_WRITEBACK) == 0) + set_bit(BDI_idle, &bdi->state); + else + clear_bit(BDI_idle, &bdi->state); } static void bdi_update_bandwidth(struct backing_dev_info *bdi, @@ -1077,13 +1135,14 @@ static void bdi_update_bandwidth(struct backing_dev_info *bdi, unsigned long dirty, unsigned long bdi_thresh, unsigned long bdi_dirty, - unsigned long start_time) + unsigned long start_time, + bool strictlimit) { if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL)) return; spin_lock(&bdi->wb.list_lock); __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty, start_time); + bdi_thresh, bdi_dirty, start_time, strictlimit); spin_unlock(&bdi->wb.list_lock); } @@ -1226,6 +1285,7 @@ static void balance_dirty_pages(struct address_space *mapping, unsigned long dirty_ratelimit; unsigned long pos_ratio; struct backing_dev_info *bdi = mapping->backing_dev_info; + bool strictlimit = test_bit(AS_STRICTLIMIT, &mapping->flags); unsigned long start_time = jiffies; for (;;) { @@ -1250,7 +1310,7 @@ static void balance_dirty_pages(struct address_space *mapping, */ freerun = dirty_freerun_ceiling(dirty_thresh, background_thresh); - if (nr_dirty <= freerun) { + if (nr_dirty <= freerun && !strictlimit) { current->dirty_paused_when = now; current->nr_dirtied = 0; current->nr_dirtied_pause = @@ -1258,7 +1318,7 @@ static void balance_dirty_pages(struct address_space *mapping, break; } - if (unlikely(!writeback_in_progress(bdi))) + if (unlikely(!writeback_in_progress(bdi)) && !strictlimit) bdi_start_background_writeback(bdi); /* @@ -1296,19 +1356,24 @@ static void balance_dirty_pages(struct address_space *mapping, bdi_stat(bdi, BDI_WRITEBACK); } + if (unlikely(!writeback_in_progress(bdi)) && + bdi_dirty > bdi_thresh / 4) + bdi_start_background_writeback(bdi); + dirty_exceeded = (bdi_dirty > bdi_thresh) && - (nr_dirty > dirty_thresh); + ((nr_dirty > dirty_thresh) || strictlimit); if (dirty_exceeded && !bdi->dirty_exceeded) bdi->dirty_exceeded = 1; bdi_update_bandwidth(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty, - start_time); + start_time, strictlimit); dirty_ratelimit = bdi->dirty_ratelimit; pos_ratio = bdi_position_ratio(bdi, dirty_thresh, background_thresh, nr_dirty, - bdi_thresh, bdi_dirty); + bdi_thresh, bdi_dirty, + strictlimit); task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> RATELIMIT_CALC_SHIFT; max_pause = bdi_max_pause(bdi, bdi_dirty); @@ -1362,6 +1427,8 @@ static void balance_dirty_pages(struct address_space *mapping, } pause: + if (unlikely(!writeback_in_progress(bdi))) + bdi_start_background_writeback(bdi); trace_balance_dirty_pages(bdi, dirty_thresh, background_thresh, @@ -2265,8 +2332,10 @@ int test_set_page_writeback(struct page *page) radix_tree_tag_set(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); - if (bdi_cap_account_writeback(bdi)) + if (bdi_cap_account_writeback(bdi)) { __inc_bdi_stat(bdi, BDI_WRITEBACK); + __inc_bdi_stat(bdi, BDI_WRITTEN_BACK); + } } if (!PageDirty(page)) radix_tree_tag_clear(&mapping->page_tree, -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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