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To: Vlastimil Babka , cl@linux.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Rientjes , Pekka Enberg , Joonsoo Kim , Oliver Glitta References: <20210831062539.898293-1-imran.f.khan@oracle.com> <20210831062539.898293-3-imran.f.khan@oracle.com> <2772cf56-4183-857f-d070-c54bceb5c8d9@suse.cz> From: imran.f.khan@oracle.com Message-ID: <2fecb5e2-1c4f-7403-7ef5-b55271bdb032@oracle.com> Date: Wed, 1 Sep 2021 16:36:32 +1000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 In-Reply-To: <2772cf56-4183-857f-d070-c54bceb5c8d9@suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SN7PR04CA0228.namprd04.prod.outlook.com (2603:10b6:806:127::23) To CO1PR10MB4468.namprd10.prod.outlook.com (2603:10b6:303:6c::24) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.191.132.27] (138.3.200.27) by SN7PR04CA0228.namprd04.prod.outlook.com (2603:10b6:806:127::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4478.19 via Frontend Transport; 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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=HxB0ciPL; dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=nvjYD+xq; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=QPLM5Poa; spf=none (imf16.hostedemail.com: domain of imran.f.khan@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=imran.f.khan@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Stat-Signature: pgag9xsh798iobdnmtzwdpxcui5o6z1o X-Rspamd-Queue-Id: 6989DF00008F X-Rspamd-Server: rspam04 X-HE-Tag: 1630478211-371997 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 31/8/21 10:06 pm, Vlastimil Babka wrote: > On 8/31/21 08:25, Imran Khan wrote: >> SLAB_STORE_USER causes information about allocating and freeing context >> of a slub object, to be stored in metadata area in a couple of struct >> track objects. These objects store allocation and/or freeing stack trace >> in an array. This may result in same stack trace getting stored in metadata >> area of multiple objects. >> STACKDEPOT can be used to store unique stack traces without any >> duplication,so use STACKDEPOT to store allocation and/or freeing stack >> traces as well. >> This results in low memory footprint, as we are not storing multiple >> copies of the same stack trace for an allocation or free. >> >> Signed-off-by: Imran Khan >> --- >> mm/slub.c | 87 ++++++++++++++++++++++++++++++------------------------- >> 1 file changed, 48 insertions(+), 39 deletions(-) >> [...] >> + >> +static void print_stack(depot_stack_handle_t stack) >> +{ >> + unsigned long *entries; >> + unsigned int nr_entries; >> + >> + nr_entries = stack_depot_fetch(stack, &entries); >> + stack_trace_print(entries, nr_entries, 0); >> +} > > This function could become part of stackdepot itself? > Okay. I have made this function part of stackdepot in my new patch set. Please see [1]. >> +#endif >> + >> static struct track *get_track(struct kmem_cache *s, void *object, >> enum track_item alloc) [...] >> @@ -4297,19 +4310,15 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) >> objp = fixup_red_left(s, objp); >> trackp = get_track(s, objp, TRACK_ALLOC); >> kpp->kp_ret = (void *)trackp->addr; >> -#ifdef CONFIG_STACKTRACE >> - for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { >> - kpp->kp_stack[i] = (void *)trackp->addrs[i]; >> - if (!kpp->kp_stack[i]) >> - break; >> - } >> +#ifdef CONFIG_STACKDEPOT >> + nr_entries = stack_depot_fetch(trackp->stack, &entries); >> + for (i = 0; i < nr_entries; i++) >> + kpp->kp_stack[i] = (void *)entries[i]; > > Hmm, in case stack_depot_save() fails and returns a zero handle (e.g. due to > enomem) this seems to rely on stack_depot_fetch() returning gracefully with > zero nr_entries for a zero handle. But I don't see such guarantee? > stack_depot_init() isn't creating such entry and stack_depot_save() doesn't > have such check. So it will work accidentally, or return garbage? But it > would be IMHO useful to add such guarantee to stackdepot one way or another. > I have addressed this scenario as well in my new patch set. Please see [1]. Since both of the changes suggested here pertain to stackdepot and are unrelated to SLUB, I have posted those changes in a separate thread [1]. >> trackp = get_track(s, objp, TRACK_FREE); >> - for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { >> - kpp->kp_free_stack[i] = (void *)trackp->addrs[i]; >> - if (!kpp->kp_free_stack[i]) >> - break; >> - } >> + nr_entries = stack_depot_fetch(trackp->stack, &entries); >> + for (i = 0; i < nr_entries; i++) >> + kpp->kp_free_stack[i] = (void *)entries[i]; >> #endif >> #endif >> } >> > [1] https://lore.kernel.org/lkml/20210901051914.971603-1-imran.f.khan@oracle.com/ Thanks for review and feedback. -- Imran