Re: limit on number of kmapped pages

2001-01-25 Thread David Wragg
"Stephen C. Tweedie" <[EMAIL PROTECTED]> writes: > On Wed, Jan 24, 2001 at 12:35:12AM +, David Wragg wrote: > > > > > And why do the pages need to be kmapped? > > > > They only need to be kmapped while data is being copied into them. > > But you only need to kmap one page at a time during

Re: limit on number of kmapped pages

2001-01-25 Thread Stephen C. Tweedie
Hi, On Wed, Jan 24, 2001 at 12:35:12AM +, David Wragg wrote: > > > And why do the pages need to be kmapped? > > They only need to be kmapped while data is being copied into them. But you only need to kmap one page at a time during the copy. There is absolutely no need to copy the whole c

Re: limit on number of kmapped pages

2001-01-24 Thread Eric W. Biederman
David Wragg <[EMAIL PROTECTED]> writes: > I'd still like to know what the basis for the current kmap limit > setting is. Mostly at one point kmap_atomic was all there was. It was only the difficulty of implementing copy_from_user with kmap_atomic that convinced people we needed something more.

Re: limit on number of kmapped pages

2001-01-24 Thread David Wragg
"Benjamin C.R. LaHaise" <[EMAIL PROTECTED]> writes: > On 24 Jan 2001, David Wragg wrote: > > > [EMAIL PROTECTED] (Eric W. Biederman) writes: > > > Why do you need such a large buffer? > > > > ext2 doesn't guarantee sustained write bandwidth (in particular, > > writing a page to an ext2 file can

Re: limit on number of kmapped pages

2001-01-23 Thread Benjamin C.R. LaHaise
On 24 Jan 2001, David Wragg wrote: > [EMAIL PROTECTED] (Eric W. Biederman) writes: > > Why do you need such a large buffer? > > ext2 doesn't guarantee sustained write bandwidth (in particular, > writing a page to an ext2 file can have a high latency due to reading > the block bitmap synchronous

Re: limit on number of kmapped pages

2001-01-23 Thread David Wragg
[EMAIL PROTECTED] (Eric W. Biederman) writes: > Why do you need such a large buffer? ext2 doesn't guarantee sustained write bandwidth (in particular, writing a page to an ext2 file can have a high latency due to reading the block bitmap synchronously). To deal with this I need at least a 2MB bu

Re: limit on number of kmapped pages

2001-01-23 Thread Eric W. Biederman
David Wragg <[EMAIL PROTECTED]> writes: > While testing some kernel code of mine on a machine with > CONFIG_HIGHMEM enabled, I've run into the limit on the number of pages > that can be kmapped at once. I was surprised to find it was so low -- > only 2MB/4MB of address space for kmap (according