> Date: Sat, 12 Mar 2022 11:35:09 +0100
> From: Martin Pieuchot <m...@openbsd.org>
>
> Try to allocate the buffer before doing the encryption, if it fails we
> do not spend time doing the encryption. This reduce the pressure when
> swapping with low memory.
>
> ok?
Makes sense to me; ok kettenis@
> Index: uvm/uvm_swap.c
> ===================================================================
> RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
> retrieving revision 1.153
> diff -u -p -r1.153 uvm_swap.c
> --- uvm/uvm_swap.c 22 Feb 2022 01:15:02 -0000 1.153
> +++ uvm/uvm_swap.c 12 Mar 2022 10:30:26 -0000
> @@ -1690,6 +1690,26 @@ uvm_swap_io(struct vm_page **pps, int st
> }
> }
>
> + /*
> + * now allocate a buf for the i/o.
> + * [make sure we don't put the pagedaemon to sleep...]
> + */
> + pflag = (async || curproc == uvm.pagedaemon_proc) ? PR_NOWAIT :
> + PR_WAITOK;
> + bp = pool_get(&bufpool, pflag | PR_ZERO);
> +
> + /*
> + * if we failed to get a swapbuf, return "try again"
> + */
> + if (bp == NULL) {
> + if (bounce) {
> + uvm_pagermapout(bouncekva, npages);
> + uvm_swap_freepages(tpps, npages);
> + }
> + uvm_pagermapout(kva, npages);
> + return (VM_PAGER_AGAIN);
> + }
> +
> /* encrypt to swap */
> if (write && bounce) {
> int i, opages;
> @@ -1729,35 +1749,6 @@ uvm_swap_io(struct vm_page **pps, int st
> PGO_PDFREECLUST);
>
> kva = bouncekva;
> - }
> -
> - /*
> - * now allocate a buf for the i/o.
> - * [make sure we don't put the pagedaemon to sleep...]
> - */
> - pflag = (async || curproc == uvm.pagedaemon_proc) ? PR_NOWAIT :
> - PR_WAITOK;
> - bp = pool_get(&bufpool, pflag | PR_ZERO);
> -
> - /*
> - * if we failed to get a swapbuf, return "try again"
> - */
> - if (bp == NULL) {
> - if (write && bounce) {
> -#ifdef UVM_SWAP_ENCRYPT
> - int i;
> -
> - /* swap encrypt needs cleanup */
> - if (encrypt)
> - for (i = 0; i < npages; i++)
> - SWAP_KEY_PUT(sdp, SWD_KEY(sdp,
> - startslot + i));
> -#endif
> -
> - uvm_pagermapout(kva, npages);
> - uvm_swap_freepages(tpps, npages);
> - }
> - return (VM_PAGER_AGAIN);
> }
>
> /*
>
>
