Re: measuring swap partition speed

void <void_at_f-m.fm> wrote on
Date: Sat, 23 Dec 2023 15:59:21 UTC :

> On Thu, 21 Dec 2023, at 17:32, Mark Millard wrote:
> > [For this message I'm replying to just the one point because I
> > expect that it is rather important to your context.]
> 
> > swapfile write requires the write request to come through the filesystem
> > write path, which might require the filesystem to allocate more memory
> > and read some data. E.g. it is known that any ZFS write request
> > allocates memory, and that write request on large UFS file might require
> > allocating and reading an indirect block buffer to find the block number
> > of the written block, if the indirect block was not yet read.
> 
> Are nfs writes the same as a "write request through the filesystem write path" ?
> If not the same, then the same deleterious effect in the context?

I expect that NFS would have the issue:

SOMETHING(s) might require NFS to allocate more memory during the attempt
to do a paging I/O of interest

But I'm no NFS expert. Basically, any additional layers that create
additional memory allocations in managing the paging I/O contribute to
such issues. The more allocations in trying to do the paging I/O, the
worse the issue. Even just the fact that umass is involved for the USB
I/O contributes some risk, if I understand right. (Seems to be rather
low risk of itself.)

===
Mark Millard
marklmi at yahoo.com