From: Jesper Dangaard Brouer <brouer@redhat.com> To: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Christoph Lameter <cl@linux.com>, akpm@linuxfoundation.org, LKML <linux-kernel@vger.kernel.org>, Linux Memory Management List <linux-mm@kvack.org>, Pekka Enberg <penberg@kernel.org>, brouer@redhat.com Subject: Re: [RFC 1/3] Slab infrastructure for array operations Date: Tue, 3 Feb 2015 23:55:12 +0100 [thread overview] Message-ID: <20150203235512.62738c3c@redhat.com> (raw) In-Reply-To: <20150129074443.GA19607@js1304-P5Q-DELUXE> On Thu, 29 Jan 2015 16:44:43 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote: > On Wed, Jan 28, 2015 at 09:30:56AM -0600, Christoph Lameter wrote: > > On Wed, 28 Jan 2015, Joonsoo Kim wrote: > > [...] > > > > The default when no options are specified is to first exhaust the node > > partial objects, then allocate new slabs as long as we have more than > > objects per page left and only then satisfy from cpu local object. I think > > that is satisfactory for the majority of the cases. > > > > The detailed control options were requested at the meeting in Auckland at > > the LCA. I am fine with dropping those if they do not make sense. Makes > > the API and implementation simpler. Jesper, are you ok with this? Yes, I'm okay with dropping the allocation flags. We might want to keep the flag "GFP_SLAB_ARRAY_FULL_COUNT" for allowing allocator to return less-than the requested elements (but I'm not 100% sure). The idea behind this is, if the allocator can "see" that it needs to perform a (relativly) expensive operation, then I would rather want it to return current elements (even if it's less than requested). As this is likely very performance sensitive code using this API. > IMHO, it'd be better to choose a proper way of allocation by slab > itself and not to expose options to API user. We could decide the > best option according to current status of kmem_cache and requested > object number and internal implementation. > > Is there any obvious example these option are needed for user? The use-cases were, if the subsystem/user know about their use-case e.g. 1) needing a large allocation which does not need to be cache hot, 2) needing a smaller (e.g 8-16 elems) allocation that should be cache hot. But, as you argue, I guess it is best to leave this up to the slab implementation as the status of the kmem_cache is only known to the allocator itself. -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer
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From: Jesper Dangaard Brouer <brouer@redhat.com> To: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Christoph Lameter <cl@linux.com>, akpm@linuxfoundation.org, LKML <linux-kernel@vger.kernel.org>, Linux Memory Management List <linux-mm@kvack.org>, Pekka Enberg <penberg@kernel.org>, brouer@redhat.com Subject: Re: [RFC 1/3] Slab infrastructure for array operations Date: Tue, 3 Feb 2015 23:55:12 +0100 [thread overview] Message-ID: <20150203235512.62738c3c@redhat.com> (raw) In-Reply-To: <20150129074443.GA19607@js1304-P5Q-DELUXE> On Thu, 29 Jan 2015 16:44:43 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote: > On Wed, Jan 28, 2015 at 09:30:56AM -0600, Christoph Lameter wrote: > > On Wed, 28 Jan 2015, Joonsoo Kim wrote: > > [...] > > > > The default when no options are specified is to first exhaust the node > > partial objects, then allocate new slabs as long as we have more than > > objects per page left and only then satisfy from cpu local object. I think > > that is satisfactory for the majority of the cases. > > > > The detailed control options were requested at the meeting in Auckland at > > the LCA. I am fine with dropping those if they do not make sense. Makes > > the API and implementation simpler. Jesper, are you ok with this? Yes, I'm okay with dropping the allocation flags. We might want to keep the flag "GFP_SLAB_ARRAY_FULL_COUNT" for allowing allocator to return less-than the requested elements (but I'm not 100% sure). The idea behind this is, if the allocator can "see" that it needs to perform a (relativly) expensive operation, then I would rather want it to return current elements (even if it's less than requested). As this is likely very performance sensitive code using this API. > IMHO, it'd be better to choose a proper way of allocation by slab > itself and not to expose options to API user. We could decide the > best option according to current status of kmem_cache and requested > object number and internal implementation. > > Is there any obvious example these option are needed for user? The use-cases were, if the subsystem/user know about their use-case e.g. 1) needing a large allocation which does not need to be cache hot, 2) needing a smaller (e.g 8-16 elems) allocation that should be cache hot. But, as you argue, I guess it is best to leave this up to the slab implementation as the status of the kmem_cache is only known to the allocator itself. -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-02-03 22:55 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-01-23 21:37 [RFC 0/3] Slab allocator array operations Christoph Lameter 2015-01-23 21:37 ` Christoph Lameter 2015-01-23 21:37 ` [RFC 1/3] Slab infrastructure for " Christoph Lameter 2015-01-23 21:37 ` Christoph Lameter 2015-01-27 8:21 ` Joonsoo Kim 2015-01-27 8:21 ` Joonsoo Kim 2015-01-27 16:57 ` Christoph Lameter 2015-01-27 16:57 ` Christoph Lameter 2015-01-28 1:33 ` Joonsoo Kim 2015-01-28 1:33 ` Joonsoo Kim 2015-01-28 15:30 ` Christoph Lameter 2015-01-28 15:30 ` Christoph Lameter 2015-01-29 7:44 ` Joonsoo Kim 2015-01-29 7:44 ` Joonsoo Kim 2015-02-03 22:55 ` Jesper Dangaard Brouer [this message] 2015-02-03 22:55 ` Jesper Dangaard Brouer 2015-01-23 21:37 ` [RFC 2/3] slub: Support " Christoph Lameter 2015-01-23 21:37 ` Christoph Lameter 2015-01-23 21:37 ` [RFC 3/3] Array alloc test code Christoph Lameter 2015-01-23 21:37 ` Christoph Lameter 2015-01-23 22:57 ` [RFC 0/3] Slab allocator array operations Andrew Morton 2015-01-23 22:57 ` Andrew Morton 2015-01-24 0:28 ` Christoph Lameter 2015-01-24 0:28 ` Christoph Lameter 2015-02-03 23:19 ` Jesper Dangaard Brouer 2015-02-03 23:19 ` Jesper Dangaard Brouer 2015-02-06 18:39 ` Christoph Lameter 2015-02-06 18:39 ` Christoph Lameter
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