Messages in this thread | | | Date | Sun, 24 Mar 2002 13:35:57 -0800 | From | Andrew Morton <> | Subject | Re: [Lse-tech] Re: 10.31 second kernel compile |
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Rogier Wolff wrote: > > ... > So we have a "PAGE_SIZE" define all around the kernel. Keep that the > same (for compatibility), but make a "REAL_PAGE_SIZE" that governs the > loop that actually sets the page table (or tlb) entries.... Note that > a first implementation may actually effectivly reduce the size of the > TLB on machines with a software loaded TLB.... > > Why would I want this? Well, suppose I have a machine that unavoidably > has to swap on some of its workload. In practise you will almost > double the disk troughput by increasing the page size by a factor of > two.
swapin and swapout already perform multipage clustering - you'd get the same benefits from increasing SWAP_CLUSTER_MAX and page_cluster.
Which is a three-line patch.
Frankly, all the discussion I've seen about altering page sizes threatens to add considerable complexity for very dubious gains. The only place where I've seen a solid justification is for scientific applications which have a huge working set, and need large pages to save on TLB thrashing.
For everything else, I believe we can get the efficiencies which we need by writing efficient code; no need to go playing with page sizes.
If someone can point at a real-world workload and say "we suck", and we can't fix that suckage without altering the page size then would that person please come forth.
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