From 235ba41c5b5adde50ec44deebcd4a5d97e2eb995 Mon Sep 17 00:00:00 2001
From: Ryo Nakamura <upa@haeena.net>
Date: Mon, 29 Apr 2024 19:36:22 +0900
Subject: [PATCH] default chunk size is filesize/(nr_conn*4) (Issue #20)

and clean-up chunk_sz related parts.
---
 doc/mscp.1.in |  6 +++++-
 doc/mscp.rst  |  6 ++++--
 src/main.c    |  2 +-
 src/mscp.c    | 14 +++-----------
 src/path.c    |  7 ++-----
 5 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/doc/mscp.1.in b/doc/mscp.1.in
index 150d1a0..3c1802e 100644
--- a/doc/mscp.1.in
+++ b/doc/mscp.1.in
@@ -198,7 +198,11 @@ parallel. The default value is 16M bytes.
 .TP
 .B \-S \fIMAX_CHUNK_SIZE\fR
 Specifies the maximum chunk size. The default is file size divided by
-the number of connections.
+the number of connections and devided by 4. If the calculated value
+is smarller than the
+.B MIN_CHUNK_SIZE
+value,
+MIN_CHUNK_SIZE is used.
 
 .TP
 .B \-a \fINR_AHEAD\fR
diff --git a/doc/mscp.rst b/doc/mscp.rst
index 41ae876..f2109f1 100644
--- a/doc/mscp.rst
+++ b/doc/mscp.rst
@@ -2,7 +2,7 @@
 MSCP
 ====
 
-:Date: v0.2.0-8-gef2dd55
+:Date: v0.2.0-9-g675126a
 
 NAME
 ====
@@ -102,7 +102,9 @@ OPTIONS
 
 **-S MAX_CHUNK_SIZE**
    Specifies the maximum chunk size. The default is file size divided by
-   the number of connections.
+   the number of connections and devided by 4. If the calculated value
+   is smarller than the **MIN_CHUNK_SIZE** value, MIN_CHUNK_SIZE is
+   used.
 
 **-a NR_AHEAD**
    Specifies the number of inflight SFTP commands. The default value is
diff --git a/src/main.c b/src/main.c
index 2e66202..d3c15fb 100644
--- a/src/main.c
+++ b/src/main.c
@@ -47,7 +47,7 @@ void usage(bool print_help)
 	       "    -R CHECKPOINT      resume transferring from the checkpoint\n"
 	       "\n"
 	       "    -s MIN_CHUNK_SIZE  min chunk size (default: 16M bytes)\n"
-	       "    -S MAX_CHUNK_SIZE  max chunk size (default: filesize/nr_conn)\n"
+	       "    -S MAX_CHUNK_SIZE  max chunk size (default: filesize/nr_conn/4)\n"
 	       "    -a NR_AHEAD        number of inflight SFTP commands (default: 32)\n"
 	       "    -b BUF_SZ          buffer size for i/o and transfer\n"
 	       "    -L LIMIT_BITRATE   Limit the bitrate, n[KMG] (default: 0, no limit)\n"
diff --git a/src/mscp.c b/src/mscp.c
index 1cb60ef..996f797 100644
--- a/src/mscp.c
+++ b/src/mscp.c
@@ -330,18 +330,10 @@ int mscp_set_dst_path(struct mscp *m, const char *dst_path)
 	return 0;
 }
 
-static int get_page_mask(void)
+static size_t get_page_mask(void)
 {
-	long page_sz = sysconf(_SC_PAGESIZE);
-	size_t page_mask = 0;
-	int n;
-
-	for (n = 0; page_sz > 0; page_sz >>= 1, n++) {
-		page_mask <<= 1;
-		page_mask |= 1;
-	}
-
-	return page_mask >> 1;
+	size_t page_sz = sysconf(_SC_PAGESIZE);
+	return ~(page_sz - 1);
 }
 
 static void mscp_stop_copy_thread(struct mscp *m)
diff --git a/src/path.c b/src/path.c
index f85e20f..140ad36 100644
--- a/src/path.c
+++ b/src/path.c
@@ -102,13 +102,10 @@ static int resolve_chunk(struct path *p, size_t size, struct path_resolve_args *
 	size_t chunk_sz, off, len;
 	size_t remaind;
 
-	if (size <= a->min_chunk_sz)
-		chunk_sz = size;
-	else if (a->max_chunk_sz)
+	if (a->max_chunk_sz)
 		chunk_sz = a->max_chunk_sz;
 	else {
-		chunk_sz = (size - (size % a->nr_conn)) / a->nr_conn;
-		chunk_sz &= ~a->chunk_align; /* align with page_sz */
+		chunk_sz = (size / (a->nr_conn * 4)) & a->chunk_align;
 		if (chunk_sz <= a->min_chunk_sz)
 			chunk_sz = a->min_chunk_sz;
 	}