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Date: Fri, 1 May 2015 19:48:20 +0200 (CEST) From: Julia Lawall <julia.lawall@...6.fr> To: "Simmons, James A." <simmonsja@...l.gov> cc: 'Julia Lawall' <Julia.Lawall@...6.fr>, Oleg Drokin <oleg.drokin@...el.com>, "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "HPDD-discuss@...ts.01.org" <HPDD-discuss@...1.01.org> Subject: RE: [HPDD-discuss] [PATCH 2/11] Staging: lustre: fld: Use kzalloc and kfree On Fri, 1 May 2015, Simmons, James A. wrote: > >From: Julia Lawall <Julia.Lawall@...6.fr> > > > >Replace OBD_ALLOC, OBD_ALLOC_WAIT, OBD_ALLOC_PTR, and OBD_ALLOC_PTR_WAIT by > >kalloc/kcalloc, and OBD_FREE and OBD_FREE_PTR by kfree. > > Nak: James Simmons <jsimmons@...radead.org> > > A simple replace will not work. The OBD_ALLOC and OBD_FREE functions allocate memory > anywhere from one page to 4MB in size. You can't use kmalloc for the 4MB allocations. > Currently lustre uses a 4 page water mark to determine if we allocate using vmalloc. Even > using kmalloc for 4 pages has shown high failure rates on some systems. It gets even more > messy with 64K page systems like ppc64 boxes. Now I'm not suggesting to port the larger > allocations to vmalloc either since issues have been founded with using vmalloc. For example > when using large stripe count files the MDS rpc generated crosses the 4 page line and vmalloc > is used. Using vmalloc caused a global spinlock to be taken which causes meta data operations > to serialized on the MDS servers. It's not the LARGE functions that do the switching? For example OBD_ALLOC ends up at __OBD_MALLOC_VERBOSE, which as far as I can see calls kmalloc (with __GFP_ZERO, and hance the use of kzalloc). julia -- 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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