From 50f3447786e09bb6c7bc4255c01a7339193a66a0 Mon Sep 17 00:00:00 2001
From: Hang Su <darcy.sh@antfin.com>
Date: Tue, 30 Jul 2019 10:53:55 +0800
Subject: Combine multiple epoll events copies
Allocate a larger memory buffer and combine multiple copies into one copy,
to reduce the number of copies from kernel memory to user memory.
Signed-off-by: Hang Su <darcy.sh@antfin.com>
---
pkg/sentry/syscalls/linux/sys_epoll.go | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
(limited to 'pkg/sentry/syscalls')
diff --git a/pkg/sentry/syscalls/linux/sys_epoll.go b/pkg/sentry/syscalls/linux/sys_epoll.go
index 4a2b9f061..65b4a227b 100644
--- a/pkg/sentry/syscalls/linux/sys_epoll.go
+++ b/pkg/sentry/syscalls/linux/sys_epoll.go
@@ -107,19 +107,20 @@ func EpollCtl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
// copyOutEvents copies epoll events from the kernel to user memory.
func copyOutEvents(t *kernel.Task, addr usermem.Addr, e []epoll.Event) error {
const itemLen = 12
- if _, ok := addr.AddLength(uint64(len(e)) * itemLen); !ok {
+ buffLen := len(e) * itemLen
+ if _, ok := addr.AddLength(uint64(buffLen)); !ok {
return syserror.EFAULT
}
- b := t.CopyScratchBuffer(itemLen)
+ b := t.CopyScratchBuffer(buffLen)
for i := range e {
- usermem.ByteOrder.PutUint32(b[0:], e[i].Events)
- usermem.ByteOrder.PutUint32(b[4:], uint32(e[i].Data[0]))
- usermem.ByteOrder.PutUint32(b[8:], uint32(e[i].Data[1]))
- if _, err := t.CopyOutBytes(addr, b); err != nil {
- return err
- }
- addr += itemLen
+ usermem.ByteOrder.PutUint32(b[i*itemLen:], e[i].Events)
+ usermem.ByteOrder.PutUint32(b[i*itemLen+4:], uint32(e[i].Data[0]))
+ usermem.ByteOrder.PutUint32(b[i*itemLen+8:], uint32(e[i].Data[1]))
+ }
+
+ if _, err := t.CopyOutBytes(addr, b); err != nil {
+ return err
}
return nil
--
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