aligned_nblks calculations broken in vm_swap.c
% Index: vm_swap.c % === % RCS file: /home/ncvs/src/sys/vm/vm_swap.c,v % retrieving revision 1.127 % retrieving revision 1.128 % diff -u -1 -r1.127 -r1.128 % --- vm_swap.c 3 Jan 2003 09:55:05 - 1.127 % +++ vm_swap.c 3 Jan 2003 14:30:46 - 1.128 % ... % @@ -353,3 +352,3 @@ %*/ % - aligned_nblks = (nblks + (dmmax - 1)) ~(u_long)(dmmax - 1); % + aligned_nblks = (nblks + dmmax_mask) ~(u_long)dmmax_mask; % % @@ -472,3 +471,3 @@ % % - aligned_nblks = (nblks + (dmmax - 1)) ~(u_long)(dmmax - 1); % + aligned_nblks = (nblks + dmmax_mask) ~(u_long)dmmax_mask; % nswap = aligned_nblks * nswdev; dmmax_mask is ~(dmmax - 1) not (dmmax - 1), so all of these changes are wrong. (New) nearby style bugs: removing the use of dmmax bogotifies a comment which refers to dmmax. (Old) related type bugs: dmmax_mask has the bogus type `int', so it is not clear how it works as a mask on machines with 32-bit ints and 64-bit block numbers. I think it works because all supported machines are 2's complement; this makes the negative value obtained by complementing the bits of (dmmax - 1) right for masking with ints, and C's integral promotion rules then make it right for masking with larger integral types too. ~(u_long)(dmmax - 1) in the old code was more careful about this, except it only works for u_long and smaller block numbers (which is enough for aligned_nblks). Bruce To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: aligned_nblks calculations broken in vm_swap.c
In message [EMAIL PROTECTED], Bruce Evans writes: % Index: vm_swap.c % === % RCS file: /home/ncvs/src/sys/vm/vm_swap.c,v % retrieving revision 1.127 % retrieving revision 1.128 % diff -u -1 -r1.127 -r1.128 % --- vm_swap.c3 Jan 2003 09:55:05 - 1.127 % +++ vm_swap.c3 Jan 2003 14:30:46 - 1.128 % ... % @@ -353,3 +352,3 @@ % */ % -aligned_nblks = (nblks + (dmmax - 1)) ~(u_long)(dmmax - 1); % +aligned_nblks = (nblks + dmmax_mask) ~(u_long)dmmax_mask; % % @@ -472,3 +471,3 @@ % % -aligned_nblks = (nblks + (dmmax - 1)) ~(u_long)(dmmax - 1); % +aligned_nblks = (nblks + dmmax_mask) ~(u_long)dmmax_mask; % nswap = aligned_nblks * nswdev; dmmax_mask is ~(dmmax - 1) not (dmmax - 1), so all of these changes are wrong. damn! Fixed, thanks! (Old) related type bugs: I'm actually more than a bit of mind to rip out the entire bogus swap-stripe code: If you want swap on a striped disk, you should use hardware, controller, vinum, ccd or raidframe to stripe. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: aligned_nblks calculations broken in vm_swap.c
Thus spake [EMAIL PROTECTED] [EMAIL PROTECTED]: I'm actually more than a bit of mind to rip out the entire bogus swap-stripe code: If you want swap on a striped disk, you should use hardware, controller, vinum, ccd or raidframe to stripe. Ccd is a nice simple solution, but by using it you lose the ability to dynamically add and remove swap and play other tricks like swap device prioritization. (Actually, prioritization would require a better abstraction for the swap subsystem anyway.) On the other hand, the static limit on the number of devices is annoying. But the point is that the swap striping code isn't entirely redundant. To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
