Re: swap cache

[Jamie Lokier]

On Mon, Dec 14, 1998 at 05:48:42PM +0330, Muthu wrote:
> It mentions that swap cache usage it to avoid one more writing if it
> is already present in swap file.  Can't this information derived from
> "dirty" bit of PTE (page table entires)?

Stephen Tweedie and all the others will explain better than I will, but
anyway: the swap cache allows *clean* pages to be in swap and memory at
the same time.

Without the swap cache, when we wanted to evict a *clean* page, we'd
have to write it to the swap file.  With the cache, it may be present in
the swap file already and we just discard it from memory.

-- Jamie