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Groups > linux.kernel > #1284532 > unrolled thread
| Started by | Pavel Machek <pavel@ucw.cz> |
|---|---|
| First post | 2015-12-05 12:20 +0100 |
| Last post | 2015-12-05 17:00 +0100 |
| Articles | 2 — 2 participants |
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Re: [PATCH v2 00/13] MADV_FREE support Pavel Machek <pavel@ucw.cz> - 2015-12-05 12:20 +0100
Re: [PATCH v2 00/13] MADV_FREE support Daniel Micay <danielmicay@gmail.com> - 2015-12-05 17:00 +0100
| From | Pavel Machek <pavel@ucw.cz> |
|---|---|
| Date | 2015-12-05 12:20 +0100 |
| Subject | Re: [PATCH v2 00/13] MADV_FREE support |
| Message-ID | <qCj2F-kX-3@gated-at.bofh.it> |
On Wed 2015-11-04 10:25:54, Minchan Kim wrote: > MADV_FREE is on linux-next so long time. The reason was two, I think. > > 1. MADV_FREE code on reclaim path was really mess. Could you explain what MADV_FREE does? Comment in code says 'free the page only when there's memory pressure'. So I mark my caches MADV_FREE, no memory pressure, I can keep using it? And if there's memory pressure, what happens? I get zeros? SIGSEGV? Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Daniel Micay <danielmicay@gmail.com> |
|---|---|
| Date | 2015-12-05 17:00 +0100 |
| Message-ID | <qCnpD-2Wd-7@gated-at.bofh.it> |
| In reply to | #1284532 |
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On 05/12/15 06:10 AM, Pavel Machek wrote: > On Wed 2015-11-04 10:25:54, Minchan Kim wrote: >> MADV_FREE is on linux-next so long time. The reason was two, I think. >> >> 1. MADV_FREE code on reclaim path was really mess. > > Could you explain what MADV_FREE does? > > Comment in code says 'free the page only when there's memory > pressure'. So I mark my caches MADV_FREE, no memory pressure, I can > keep using it? And if there's memory pressure, what happens? I get > zeros? SIGSEGV? You get zeroes. It's not designed for that use case right now. It's for malloc implementations to use internally. There would need to be a new feature like MADV_FREE_UNDO for it to be usable for caches and it may make more sense for that to be a separate feature entirely, i.e. have a different flag for marking too (not sure) since it wouldn't need to worry about whether stuff is touched.
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