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Thu, 4 Apr 2024 13:22:21 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap2.dmz-prg2.suse.org with ESMTPSA id 8llLNo2pDmYbcgAAn2gu4w (envelope-from ); Thu, 04 Apr 2024 13:22:21 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 844AEA0816; Thu, 4 Apr 2024 15:22:21 +0200 (CEST) Date: Thu, 4 Apr 2024 15:22:21 +0200 From: Jan Kara To: Kemeng Shi Cc: tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, jack@suse.cz, ojaswin@linux.ibm.com, ritesh.list@gmail.com Subject: Re: [PATCH 1/5] ext4: keep "prefetch_grp" and "nr" consistent Message-ID: <20240404132221.uliif3mw7acy7t7l@quack3> References: <20240326213823.528302-1-shikemeng@huaweicloud.com> <20240326213823.528302-2-shikemeng@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240326213823.528302-2-shikemeng@huaweicloud.com> X-Spam-Flag: NO X-Spam-Score: 0.70 X-Spam-Level: X-Spamd-Result: default: False [0.70 / 50.00]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; BAYES_HAM(-0.00)[39.50%]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_THREE(0.00)[3]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[mit.edu,dilger.ca,vger.kernel.org,suse.cz,linux.ibm.com,gmail.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_TLS_LAST(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,suse.cz:email] On Wed 27-03-24 05:38:19, Kemeng Shi wrote: > Keep "prefetch_grp" and "nr" consistent to avoid to call > ext4_mb_prefetch_fini with non-prefetched groups. > When we step into next criteria, "prefetch_grp" is set to prefetch start > of new criteria while "nr" is number of the prefetched group in previous > criteria. If previous criteria and next criteria are both inexpensive > (< CR_GOAL_LEN_SLOW) and prefetch_ios reachs sbi->s_mb_prefetch_limit > in previous criteria, "prefetch_grp" and "nr" will be inconsistent and > may introduce unexpected cost to do ext4_mb_init_group for non-prefetched > groups. > Reset "nr" to 0 when we reset "prefetch_grp" to start of prefech in next > criteria to ensure "prefetch_grp" and "nr" are consistent. > > Signed-off-by: Kemeng Shi Looks good. Feel free to add: Reviewed-by: Jan Kara Honza > --- > fs/ext4/mballoc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > index 12b3f196010b..a61fc52956b2 100644 > --- a/fs/ext4/mballoc.c > +++ b/fs/ext4/mballoc.c > @@ -2856,6 +2856,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) > group = ac->ac_g_ex.fe_group; > ac->ac_groups_linear_remaining = sbi->s_mb_max_linear_groups; > prefetch_grp = group; > + nr = 0; > > for (i = 0, new_cr = cr; i < ngroups; i++, > ext4_mb_choose_next_group(ac, &new_cr, &group, ngroups)) { > -- > 2.30.0 > -- Jan Kara SUSE Labs, CR