[PATCH] blkparse: cut down on excessive number of fcntl() calls

Cache the blocking state locally and only issue it if changed.

diff --git a/blkparse.c b/blkparse.c
index 5af31a7ae69e9b5832445f728409372412411531..8a90362c25454e865048618f180f3ccb4532a7b2 100644 (file)
--- a/blkparse.c
+++ b/blkparse.c
@@ -1701,17 +1701,22 @@ static void show_entries_rb(int force)
        }
 }
 
-static int read_data(int fd, void *buffer, int bytes, int block)
+static int read_data(int fd, void *buffer, int bytes, int block, int *fdblock)
 {
        int ret, bytes_left, fl;
        void *p;
 
-       fl = fcntl(fd, F_GETFL);
+       if (block != *fdblock) {
+               fl = fcntl(fd, F_GETFL);
 
-       if (!block)
-               fcntl(fd, F_SETFL, fl | O_NONBLOCK);
-       else
-               fcntl(fd, F_SETFL, fl & ~O_NONBLOCK);
+               if (!block) {
+                       *fdblock = 0;
+                       fcntl(fd, F_SETFL, fl | O_NONBLOCK);
+               } else {
+                       *fdblock = 1;
+                       fcntl(fd, F_SETFL, fl & ~O_NONBLOCK);
+               }
+       }
 
        bytes_left = bytes;
        p = buffer;
@@ -1742,7 +1747,7 @@ static int read_data(int fd, void *buffer, int bytes, int block)
        return 0;
 }
 
-static int read_events(int fd, int always_block)
+static int read_events(int fd, int always_block, int *fdblock)
 {
        struct per_dev_info *pdi = NULL;
        unsigned int events = 0;
@@ -1750,12 +1755,14 @@ static int read_events(int fd, int always_block)
        while (!is_done() && events < rb_batch) {
                struct blk_io_trace *bit;
                struct trace *t;
-               int pdu_len;
+               int pdu_len, should_block;
                __u32 magic;
 
                bit = bit_alloc();
 
-               if (read_data(fd, bit, sizeof(*bit), !events || always_block)) {
+               should_block = !events || always_block;
+
+               if (read_data(fd, bit, sizeof(*bit), should_block, fdblock)) {
                        bit_free(bit);
                        break;
                }
@@ -1770,7 +1777,7 @@ static int read_events(int fd, int always_block)
                if (pdu_len) {
                        void *ptr = realloc(bit, sizeof(*bit) + pdu_len);
 
-                       if (read_data(fd, ptr + sizeof(*bit), pdu_len, 1)) {
+                       if (read_data(fd, ptr + sizeof(*bit), pdu_len, 1, fdblock)) {
                                bit_free(ptr);
                                break;
                        }
@@ -1826,6 +1833,7 @@ static int do_file(void)
                        pci = get_cpu_info(pdi, j);
                        pci->cpu = j;
                        pci->fd = -1;
+                       pci->fdblock = -1;
        
                        p = strdup(pdi->name);
                        dname = dirname(p);
@@ -1877,7 +1885,7 @@ static int do_file(void)
                                if (pci->fd == -1)
                                        continue;
 
-                               events = read_events(pci->fd, 1);
+                               events = read_events(pci->fd, 1, &pci->fdblock);
                                if (!events) {
                                        cpu_mark_offline(pdi, pci->cpu);
                                        close(pci->fd);
@@ -1911,7 +1919,7 @@ static int do_file(void)
 static int do_stdin(void)
 {
        unsigned long long youngest;
-       int fd, events;
+       int fd, events, fdblock;
 
        last_allowed_time = -1ULL;
        fd = dup(STDIN_FILENO);
@@ -1920,7 +1928,8 @@ static int do_stdin(void)
                return -1;
        }
 
-       while ((events = read_events(fd, 0)) != 0) {
+       fdblock = -1;
+       while ((events = read_events(fd, 0, &fdblock)) != 0) {
        
                smallest_seq_read = -1U;
 

diff --git a/blktrace.h b/blktrace.h
index 046a1aaf1db67becd5551a05e0a0dfd11322f567..7462edc3fcd13e00dd58e91b65a9f29a005798d0 100644 (file)
--- a/blktrace.h
+++ b/blktrace.h
@@ -37,6 +37,7 @@ struct per_cpu_info {
        unsigned int nelems;
 
        int fd;
+       int fdblock;
        char fname[128];
 
        struct io_stats io_stats;