Messages in this thread | | | Date | Wed, 06 Jan 2010 19:10:02 +0530 | From | Nitin Gupta <> | Subject | Re: [PATCH 1/2] [mmotm] Add swap slot free callback to block_device_operations |
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On 01/05/2010 04:28 PM, Hugh Dickins wrote: > On Tue, 5 Jan 2010, Nitin Gupta wrote: > >> This callback is required when RAM based devices are >> used as swap disks. One such device is ramzswap[1] which >> is used as compressed in-memory swap disk. For such >> devices, we need a callback as soon as a swap slot is no >> longer used to allow freeing memory allocated for this >> slot. Without this callback, stale data can quickly >> accumulate in memory defeating the whole purpose of >> such devices. >> >> Another user of this callback will be "preswap" as >> introduced by "Transcendent Memory" patches: >> http://lwn.net/Articles/367286/ >> (I intend to integrade preswap with ramzswap). >> >> [1] ramzswap: http://code.google.com/p/compcache/ >> >> Signed-off-by: Nitin Gupta <ngupta@vflare.org> > > Yes, thanks for your patience in putting this together: > I much prefer this version to all the other ways considered. >
> (Though you should later add a comment, pointing out that this > callback is with swap_lock and often page table lock also held.) >
I will send another patch for this.
> We know that's unsatisfactory, but it is the nature of swap: > cutting some corners to get the job done without allocating > more memory. Having tried myself to do proper discard at > swap_free time, I know that is hard: and I believe you've > made the right decision to do it in this way for ramzswap. > > Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> >
Thanks for the review. So, is this now going in mmotm tree?
Nitin
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