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Date: Fri, 11 May 2012 09:25:43 +0900 From: Minchan Kim <minchan@...nel.org> To: Dan Magenheimer <dan.magenheimer@...cle.com> CC: Nitin Gupta <ngupta@...are.org>, Pekka Enberg <penberg@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Seth Jennings <sjenning@...ux.vnet.ibm.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, cl@...ux-foundation.org Subject: Re: [PATCH 4/4] zsmalloc: zsmalloc: align cache line size On 05/11/2012 09:03 AM, Dan Magenheimer wrote: >> From: Minchan Kim [mailto:minchan@...nel.org] >> Subject: Re: [PATCH 4/4] zsmalloc: zsmalloc: align cache line size >> >> On 05/08/2012 11:00 PM, Dan Magenheimer wrote: >> >>>> From: Minchan Kim [mailto:minchan@...nel.org] >>>>> zcache can potentially create a lot of pools, so the latter will save >>>>> some memory. >>>> >>>> >>>> Dumb question. >>>> Why should we create pool per user? >>>> What's the problem if there is only one pool in system? >>> >>> zcache doesn't use zsmalloc for cleancache pages today, but >>> that's Seth's plan for the future. Then if there is a >>> separate pool for each cleancache pool, when a filesystem >>> is umount'ed, it isn't necessary to walk through and delete >>> all pages one-by-one, which could take quite awhile. >> >>> >> >>> ramster needs one pool for each client (i.e. machine in the >>> cluster) for frontswap pages for the same reason, and >>> later, for cleancache pages, one per mounted filesystem >>> per client >> >> >> Fair enough. >> But some subsystems can't want a own pool for not waste unnecessary memory. >> >> Then, how about this interfaces like slab? >> >> 1. zs_handle zs_malloc(size_t size, gfp_t flags) - share a pool by many subsystem(like kmalloc) >> 2. zs_handle zs_malloc_pool(struct zs_pool *pool, size_t size) - use own pool(like kmem_cache_alloc) >> >> Any thoughts? > > I don't have any objections to adding this kind of > capability to zsmalloc. But since we are just speculating > that this capability would be used by some future > kernel subsystem, isn't it normal kernel protocol for > this new capability NOT to be added until that future > kernel subsystem creates a need for it. Now zram makes pool per block device and a embedded system may use zram for several block device, ex) swap device, several compressed tmpfs In such case, share pool is better than private pool because embedded system don't mount/umount frequently on such directories since booting. > > As I said in reply to the other thread, there is missing > functionality in zsmalloc that is making it difficult for > it to be used by zcache. It would be good if Seth > and Nitin (and any other kernel developers) would work So, if you guys post TODO list, it helps fix the direction. > on those issues before adding capabilities for non-existent > future users of zsmalloc. I think it's not urgent than zs_handle mess. > > Again, that's just my opinion. > Dan > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@...ck.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: <a href=ilto:"dont@...ck.org"> email@...ck.org </a> > -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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