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Mon, 13 Oct 2025 06:33:38 +0000 Message-ID: <359e3d8f-4db7-4430-8520-4fed9de4f48e@suse.de> Date: Mon, 13 Oct 2025 08:33:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCHv2 4/4] nvme-multipath: add debugfs attribute for adaptive I/O policy stat To: Nilay Shroff , linux-nvme@lists.infradead.org Cc: kbusch@kernel.org, hch@lst.de, axboe@kernel.dk, dwagner@suse.de, gjoyce@ibm.com References: <20251009100608.1699550-1-nilay@linux.ibm.com> <20251009100608.1699550-5-nilay@linux.ibm.com> Content-Language: en-US From: Hannes Reinecke In-Reply-To: <20251009100608.1699550-5-nilay@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7735E1F460 X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim,suse.de:mid,suse.de:email]; DKIM_TRACE(0.00)[suse.de:+] X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251012_233340_285099_83346D96 X-CRM114-Status: GOOD ( 10.60 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 10/9/25 12:05, Nilay Shroff wrote: > This commit introduces a new debugfs attribute, "adaptive_stat", under > both per-path and head debugfs directories (defined under /sys/kernel/ > debug/block/). This attribute provides visibility into the internal > state of the adaptive I/O policy to aid in debugging and performance > analysis. > > For per-path entries, "adaptive_stat" reports the corresponding path > statistics such as I/O weight, selection count, processed samples, and > ignored samples. > > For head entries, it reports per-CPU statistics for each reachable path, > including I/O weight, path score, smoothed (EWMA) latency, selection > count, processed samples, and ignored samples. > > These additions enhance observability of the adaptive I/O path selection > behavior and help diagnose imbalance or instability in multipath > performance. > > Signed-off-by: Nilay Shroff > --- > drivers/nvme/host/core.c | 3 + > drivers/nvme/host/debugfs.c | 117 ++++++++++++++++++++++++++++++++++ > drivers/nvme/host/multipath.c | 2 + > 3 files changed, 122 insertions(+) > Reviewed-by: Hannes Reinecke Might be an idea to have support for queue-depth in here, too. Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich