From: Nathan Zimmer <nzimmer@sgi.com> To: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Travis <travis@sgi.com>, Nathan Zimmer <nzimmer@sgi.com>, Peter Anvin <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Robin Holt <holt@sgi.com>, Rob Landley <rob@landley.net>, Daniel J Blueman <daniel@numascale-asia.com>, Andrew Morton <akpm@linux-foundation.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Yinghai Lu <yinghai@kernel.org>, Mel Gorman <mgorman@suse.de> Subject: Re: [RFC v3 0/5] Transparent on-demand struct page initialization embedded in the buddy allocator Date: Tue, 13 Aug 2013 18:10:20 -0500 [thread overview] Message-ID: <20130813231020.GA22667@asylum.americas.sgi.com> (raw) In-Reply-To: <CA+55aFwRHdQ_f6ryUU1yWkW1Qz8cG958jLZuyhd_YdOq4-rfRA@mail.gmail.com> On Tue, Aug 13, 2013 at 10:51:37AM -0700, Linus Torvalds wrote: > I realize that benchmarking cares, and yes, I also realize that some > benchmarks actually want to reboot the machine between some runs just > to get repeatability, but if you're benchmarking a 16TB machine I'm > guessing any serious benchmark that actually uses that much memory is > going to take many hours to a few days to run anyway? Having some way > to wait until the memory is all done (which might even be just a silly > shell script that does "ps" and waits for the kernel threads to all go > away) isn't going to kill the benchmark - and the benchmark itself > will then not have to worry about hittinf the "oops, I need to > initialize 2GB of RAM now because I hit an uninitialized page". > I am not overly concerned with cost having to setup a page struct on first touch but what I need to avoid is adding more permanent cost to page faults on a system that is already "primed". > Ok, so I don't know all the issues, and in many ways I don't even > really care. You could do it other ways, I don't think this is a big > deal. The part I hate is the runtime hook into the core MM page > allocation code, so I'm just throwing out any random thing that comes > to my mind that could be used to avoid that part. > The only mm structure we are adding to is a new flag in page->flags. That didn't seem too much. I had hoped to restrict the core mm changes to check_new_page and free_pages_check but I haven't gotten there yet. Not putting on uninitialized pages on to the lru would work but then I would be concerned over any calculations based on totalpages. I might be too paranoid there but having that be incorrect until after a system is booted worries me. Nate
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From: Nathan Zimmer <nzimmer@sgi.com> To: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Travis <travis@sgi.com>, Nathan Zimmer <nzimmer@sgi.com>, Peter Anvin <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Robin Holt <holt@sgi.com>, Rob Landley <rob@landley.net>, Daniel J Blueman <daniel@numascale-asia.com>, Andrew Morton <akpm@linux-foundation.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Yinghai Lu <yinghai@kernel.org>, Mel Gorman <mgorman@suse.de> Subject: Re: [RFC v3 0/5] Transparent on-demand struct page initialization embedded in the buddy allocator Date: Tue, 13 Aug 2013 18:10:20 -0500 [thread overview] Message-ID: <20130813231020.GA22667@asylum.americas.sgi.com> (raw) In-Reply-To: <CA+55aFwRHdQ_f6ryUU1yWkW1Qz8cG958jLZuyhd_YdOq4-rfRA@mail.gmail.com> On Tue, Aug 13, 2013 at 10:51:37AM -0700, Linus Torvalds wrote: > I realize that benchmarking cares, and yes, I also realize that some > benchmarks actually want to reboot the machine between some runs just > to get repeatability, but if you're benchmarking a 16TB machine I'm > guessing any serious benchmark that actually uses that much memory is > going to take many hours to a few days to run anyway? Having some way > to wait until the memory is all done (which might even be just a silly > shell script that does "ps" and waits for the kernel threads to all go > away) isn't going to kill the benchmark - and the benchmark itself > will then not have to worry about hittinf the "oops, I need to > initialize 2GB of RAM now because I hit an uninitialized page". > I am not overly concerned with cost having to setup a page struct on first touch but what I need to avoid is adding more permanent cost to page faults on a system that is already "primed". > Ok, so I don't know all the issues, and in many ways I don't even > really care. You could do it other ways, I don't think this is a big > deal. The part I hate is the runtime hook into the core MM page > allocation code, so I'm just throwing out any random thing that comes > to my mind that could be used to avoid that part. > The only mm structure we are adding to is a new flag in page->flags. That didn't seem too much. I had hoped to restrict the core mm changes to check_new_page and free_pages_check but I haven't gotten there yet. Not putting on uninitialized pages on to the lru would work but then I would be concerned over any calculations based on totalpages. I might be too paranoid there but having that be incorrect until after a system is booted worries me. Nate -- 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:[~2013-08-13 23:10 UTC|newest] Thread overview: 153+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-07-12 2:03 [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator Robin Holt 2013-07-12 2:03 ` Robin Holt 2013-07-12 2:03 ` [RFC 1/4] memblock: Introduce a for_each_reserved_mem_region iterator Robin Holt 2013-07-12 2:03 ` Robin Holt 2013-07-12 2:03 ` [RFC 2/4] Have __free_pages_memory() free in larger chunks Robin Holt 2013-07-12 2:03 ` Robin Holt 2013-07-12 7:45 ` Robin Holt 2013-07-12 7:45 ` Robin Holt 2013-07-13 3:08 ` Yinghai Lu 2013-07-13 3:08 ` Yinghai Lu 2013-07-16 13:02 ` Sam Ben 2013-07-16 13:02 ` Sam Ben 2013-07-23 15:32 ` Johannes Weiner 2013-07-23 15:32 ` Johannes Weiner 2013-07-12 2:03 ` [RFC 3/4] Seperate page initialization into a separate function Robin Holt 2013-07-12 2:03 ` Robin Holt 2013-07-13 3:06 ` Yinghai Lu 2013-07-13 3:06 ` Yinghai Lu 2013-07-15 3:19 ` Robin Holt 2013-07-15 3:19 ` Robin Holt 2013-07-12 2:03 ` [RFC 4/4] Sparse initialization of struct page array Robin Holt 2013-07-12 2:03 ` Robin Holt 2013-07-13 4:19 ` Yinghai Lu 2013-07-13 4:19 ` Yinghai Lu 2013-07-13 4:39 ` H. Peter Anvin 2013-07-13 4:39 ` H. Peter Anvin 2013-07-13 5:31 ` Yinghai Lu 2013-07-13 5:31 ` Yinghai Lu 2013-07-13 5:38 ` H. Peter Anvin 2013-07-13 5:38 ` H. Peter Anvin 2013-07-15 14:08 ` Nathan Zimmer 2013-07-15 14:08 ` Nathan Zimmer 2013-07-15 17:45 ` Nathan Zimmer 2013-07-15 17:45 ` Nathan Zimmer 2013-07-15 17:54 ` H. Peter Anvin 2013-07-15 17:54 ` H. Peter Anvin 2013-07-15 18:26 ` Robin Holt 2013-07-15 18:26 ` Robin Holt 2013-07-15 18:29 ` H. Peter Anvin 2013-07-15 18:29 ` H. Peter Anvin 2013-07-23 8:32 ` Ingo Molnar 2013-07-23 8:32 ` Ingo Molnar 2013-07-23 11:09 ` Robin Holt 2013-07-23 11:09 ` Robin Holt 2013-07-23 11:15 ` Robin Holt 2013-07-23 11:15 ` Robin Holt 2013-07-23 11:41 ` Robin Holt 2013-07-23 11:41 ` Robin Holt 2013-07-23 11:50 ` Robin Holt 2013-07-23 11:50 ` Robin Holt 2013-07-16 10:26 ` Robin Holt 2013-07-16 10:26 ` Robin Holt 2013-07-25 2:25 ` Robin Holt 2013-07-25 2:25 ` Robin Holt 2013-07-25 12:50 ` Yinghai Lu 2013-07-25 12:50 ` Yinghai Lu 2013-07-25 13:42 ` Robin Holt 2013-07-25 13:42 ` Robin Holt 2013-07-25 13:52 ` Yinghai Lu 2013-07-25 13:52 ` Yinghai Lu 2013-07-15 21:30 ` Andrew Morton 2013-07-15 21:30 ` Andrew Morton 2013-07-16 10:38 ` Robin Holt 2013-07-16 10:38 ` Robin Holt 2013-07-12 8:27 ` [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator Ingo Molnar 2013-07-12 8:27 ` Ingo Molnar 2013-07-12 8:47 ` boot tracing Borislav Petkov 2013-07-12 8:47 ` Borislav Petkov 2013-07-12 8:53 ` Ingo Molnar 2013-07-12 8:53 ` Ingo Molnar 2013-07-15 1:38 ` Sam Ben 2013-07-15 1:38 ` Sam Ben 2013-07-23 8:18 ` Ingo Molnar 2013-07-23 8:18 ` Ingo Molnar 2013-07-12 9:19 ` [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator Robert Richter 2013-07-12 9:19 ` Robert Richter 2013-07-15 15:16 ` Robin Holt 2013-07-15 15:16 ` Robin Holt 2013-07-16 8:55 ` Joonsoo Kim 2013-07-16 8:55 ` Joonsoo Kim 2013-07-16 9:08 ` Borislav Petkov 2013-07-16 9:08 ` Borislav Petkov 2013-07-23 8:20 ` Ingo Molnar 2013-07-23 8:20 ` Ingo Molnar 2013-07-15 15:00 ` Robin Holt 2013-07-15 15:00 ` Robin Holt 2013-07-17 5:17 ` Sam Ben 2013-07-17 5:17 ` Sam Ben 2013-07-17 9:30 ` Robin Holt 2013-07-17 9:30 ` Robin Holt 2013-07-19 23:51 ` Yinghai Lu 2013-07-22 6:13 ` Robin Holt 2013-07-22 6:13 ` Robin Holt 2013-08-02 17:44 ` [RFC v2 0/5] " Nathan Zimmer 2013-08-02 17:44 ` Nathan Zimmer 2013-08-02 17:44 ` [RFC v2 1/5] memblock: Introduce a for_each_reserved_mem_region iterator Nathan Zimmer 2013-08-02 17:44 ` Nathan Zimmer 2013-08-02 17:44 ` [RFC v2 2/5] Have __free_pages_memory() free in larger chunks Nathan Zimmer 2013-08-02 17:44 ` Nathan Zimmer 2013-08-02 17:44 ` [RFC v2 3/5] Move page initialization into a separate function Nathan Zimmer 2013-08-02 17:44 ` Nathan Zimmer 2013-08-02 17:44 ` [RFC v2 4/5] Only set page reserved in the memblock region Nathan Zimmer 2013-08-02 17:44 ` Nathan Zimmer 2013-08-03 20:04 ` Nathan Zimmer 2013-08-03 20:04 ` Nathan Zimmer 2013-08-02 17:44 ` [RFC v2 5/5] Sparse initialization of struct page array Nathan Zimmer 2013-08-02 17:44 ` Nathan Zimmer 2013-08-05 9:58 ` [RFC v2 0/5] Transparent on-demand struct page initialization embedded in the buddy allocator Ingo Molnar 2013-08-05 9:58 ` Ingo Molnar 2013-08-12 21:54 ` [RFC v3 " Nathan Zimmer 2013-08-12 21:54 ` Nathan Zimmer 2013-08-12 21:54 ` [RFC v3 1/5] memblock: Introduce a for_each_reserved_mem_region iterator Nathan Zimmer 2013-08-12 21:54 ` Nathan Zimmer 2013-08-12 21:54 ` [RFC v3 2/5] Have __free_pages_memory() free in larger chunks Nathan Zimmer 2013-08-12 21:54 ` Nathan Zimmer 2013-08-12 21:54 ` [RFC v3 3/5] Move page initialization into a separate function Nathan Zimmer 2013-08-12 21:54 ` Nathan Zimmer 2013-08-12 21:54 ` [RFC v3 4/5] Only set page reserved in the memblock region Nathan Zimmer 2013-08-12 21:54 ` Nathan Zimmer 2013-08-12 21:54 ` [RFC v3 5/5] Sparse initialization of struct page array Nathan Zimmer 2013-08-12 21:54 ` Nathan Zimmer 2013-08-13 10:58 ` [RFC v3 0/5] Transparent on-demand struct page initialization embedded in the buddy allocator Ingo Molnar 2013-08-13 10:58 ` Ingo Molnar 2013-08-13 17:09 ` Linus Torvalds 2013-08-13 17:09 ` Linus Torvalds 2013-08-13 17:23 ` H. Peter Anvin 2013-08-13 17:23 ` H. Peter Anvin 2013-08-13 17:33 ` Mike Travis 2013-08-13 17:33 ` Mike Travis 2013-08-13 17:51 ` Linus Torvalds 2013-08-13 17:51 ` Linus Torvalds 2013-08-13 18:04 ` Mike Travis 2013-08-13 18:04 ` Mike Travis 2013-08-13 19:06 ` Mike Travis 2013-08-13 19:06 ` Mike Travis 2013-08-13 20:24 ` Yinghai Lu 2013-08-13 20:24 ` Yinghai Lu 2013-08-13 20:37 ` Mike Travis 2013-08-13 20:37 ` Mike Travis 2013-08-13 21:35 ` Nathan Zimmer 2013-08-13 21:35 ` Nathan Zimmer 2013-08-13 23:10 ` Nathan Zimmer [this message] 2013-08-13 23:10 ` Nathan Zimmer 2013-08-13 23:55 ` Linus Torvalds 2013-08-13 23:55 ` Linus Torvalds 2013-08-14 11:27 ` Ingo Molnar 2013-08-14 11:27 ` Ingo Molnar 2013-08-14 11:05 ` Ingo Molnar 2013-08-14 11:05 ` Ingo Molnar 2013-08-14 22:15 ` Nathan Zimmer 2013-08-14 22:15 ` Nathan Zimmer 2013-08-16 16:36 ` Dave Hansen 2013-08-16 16:36 ` Dave Hansen
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