From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jack Steiner Date: Thu, 13 Nov 2003 03:18:01 +0000 Subject: Re: Inefficient TLB flushing Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Wed, Nov 12, 2003 at 01:22:53PM -0800, Andrew Morton wrote: > David Mosberger wrote: > > > > Jack> Here is the patch that I am currently testing: > > > > Jack> --- /usr/tmp/TmpDir.19957-0/linux/mm/memory.c_1.79 Wed Nov 12 13:56:25 2003 > > Jack> +++ linux/mm/memory.c Wed Nov 12 12:57:25 2003 > > Jack> @@ -574,9 +574,10 @@ > > Jack> if ((long)zap_bytes > 0) > > Jack> continue; > > Jack> if (need_resched()) { > > Jack> + int fullmm = (*tlbp)->fullmm; > > Jack> tlb_finish_mmu(*tlbp, tlb_start, start); > > Jack> cond_resched_lock(&mm->page_table_lock); > > Jack> - *tlbp = tlb_gather_mmu(mm, 0); > > Jack> + *tlbp = tlb_gather_mmu(mm, fullmm); > > Jack> tlb_start_valid = 0; > > Jack> } > > Jack> zap_bytes = ZAP_BLOCK_SIZE; > > > > I think the patch will work fine, but it's not very clean, because it > > bypasses the TLB-flush API and directly accesses > > implementation-specific internals. Perhaps it would be better to pass > > a "fullmm" flag to unmap_vmas(). Andrew? > > Either that, or add a new interface function > > int mmu_gather_is_full_mm(mmu_gather *tlb); > > and use it... > How implementation independent should it be? Currently, there is only one field in the mmu_gather structure that must be preserved. However, if we want to make the interface truly implementation independent, it seems like we should define something like: if (need_resched()) { struct mmu_gather_state state; tlb_mmu_gather_save_state(*tlbp, &state); tlb_finish_mmu(*tlbp, tlb_start, start); ... *tlbp = tlb_mmu_gather_restore_state(&state); } Is this overkill? Should we use the patch given above for 2.6.0 & replace it with an implementation independent interface for 2.6.1? -- Thanks Jack Steiner (steiner@sgi.com) 651-683-5302 Principal Engineer SGI - Silicon Graphics, Inc.