d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

- Use a separate sx lock to try to limit the number of concurrent userland

Browse Source 
sysctl requests to avoid wiring too much user memory.  Only grab this
  lock if the user's old buffer is larger than a page as a tradeoff to
  allow more concurrency for common small requests.
- Just use a shared lock on the sysctl tree for user sysctl requests now.

MFC after:	1 week
This commit is contained in:
John Baldwin 2009-05-14 22:01:32 +00:00
parent 76dae09449
commit 3e829b18d6
1 changed files with 16 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
sys/kern/kern_sysctl.c
View File

@ -77,11 +77,12 @@ static MALLOC_DEFINE(M_SYSCTLTMP, "sysctltmp", "sysctl temp output buffer");
* API rather than using the dynamic API. Use of the dynamic API is
* strongly encouraged for most code.
*
* This lock is also used to serialize userland sysctl requests. Some
* sysctls wire user memory, and serializing the requests limits the
* amount of wired user memory in use.
* The sysctlmemlock is used to limit the amount of user memory wired for
* sysctl requests. This is implemented by serializing any userland
* sysctl requests larger than a single page via an exclusive lock.
*/
static struct sx sysctllock;
static struct sx sysctlmemlock;
#define SYSCTL_SLOCK() sx_slock(&sysctllock)
#define SYSCTL_SUNLOCK() sx_sunlock(&sysctllock)
@ -543,6 +544,7 @@ sysctl_register_all(void *arg)
{
struct sysctl_oid **oidp;
sx_init(&sysctlmemlock, "sysctl mem");
SYSCTL_INIT();
SYSCTL_XLOCK();
SET_FOREACH(oidp, sysctl_set)
@ -1565,7 +1567,7 @@ userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
size_t *oldlenp, int inkernel, void *new, size_t newlen, size_t *retval,
int flags)
{
int error = 0;
int error = 0, memlocked;
struct sysctl_req req;
bzero(&req, sizeof req);
@ -1605,14 +1607,20 @@ userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
if (KTRPOINT(curthread, KTR_SYSCTL))
ktrsysctl(name, namelen);
#endif
SYSCTL_XLOCK();
if (req.oldlen > PAGE_SIZE) {
memlocked = 1;
sx_xlock(&sysctlmemlock);
} else
memlocked = 0;
CURVNET_SET(TD_TO_VNET(curthread));
for (;;) {
req.oldidx = 0;
req.newidx = 0;
SYSCTL_SLOCK();
error = sysctl_root(0, name, namelen, &req);
SYSCTL_SUNLOCK();
if (error != EAGAIN)
break;
uio_yield();
@ -1622,7 +1630,8 @@ userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
if (req.lock == REQ_WIRED && req.validlen > 0)
vsunlock(req.oldptr, req.validlen);
SYSCTL_XUNLOCK();
if (memlocked)
sx_xunlock(&sysctlmemlock);
if (error && error != ENOMEM)
return (error);